The end of the story in Kaladesh, before Aether Revolt starts seems to be Tezzeret confiscating everyone's inventions. This I suspect will lead to the Aether Revolt with possibly Saheeli Rai taking up the inventors cause to get their inventions back.
What Tezzeret wants from amongst the inventions I'm not sure about, but it is most definitely not for the good of everyone and I suspect it will be something for Bolas.
Not only is it the Egyptian themed black everyone was expecting, Nicol Bolas returns! I wonder what his machinations will be this time, and how will the Gatewatch deal with a plane of Nicol Bolas worshippers? Find out at your local card store in April, 2017!
So from what we know from various sources the following Planeswalkers are on Kaladesh:
Saheeli Rai - RU
Dovin Baan - U
Nissa Revane - G
Chandra Nalaar - R
Liliana Vess - B
I'm guessing that we won't get a second Liliana card so close to Eldritch Moon and that she'll be in the background of the story but won't get a card. This means that we are missing a white and a black planeswalker in our list. Now we haven't yet seen the villain who is sabotaging things, so its probable that there will be another Planeswalker in Aether Revolt who is revealed to be responsible. The Gremlins in the past have been black aligned, so I'm guessing that the hidden villain will be black aligned who is stirring up the rebels.
I also wonder if both Chandra's parents really died twelve years ago. They have deliberately left things vague.
Whilst Kaladesh will certainly have its share of artifact mechanics, I feel that not all of them will be artifact related. Kaladesh is about Aether and inventing as well as artifacts, but green (which notably hates artifacts) must have some role to play in the block.
We 'know' that mechanic E is most probably the vehicle mechanic. I would expect perhaps one more artifact related mechanic. However I would expect that Green will have a mechanic that will not be artifact based but will be on the side of the rebels.
Also the mechanics are usually restricted to certain colours in the colour pie. I wonder if the mechanics in this set will be more based around enemy coloured pairs giving us:-
Red / Blue - Inventors
White /Black - Consuls
Red / White - Consul's forces
Blue / Green - shapers of the Aether
Green / Black - rebels
What we know of Kaladesh so far (from Magic Origins) is that it is ruled by the Consuls who are blue white. May of the inventors seem to be blue-red in nature. Outside of the cities there are natural things such as Caterpillars, and Tigers. Also the villagers seem to be pretty green in nature. So I would expect lots of wild animals for one. I wonder (as it is indian themed) whether we will get Loxodon there are well in Green-white.
As to black. We haven't seen anything of black so far in Kaladesh. I wonder if the Consuls have a black component to them, making them Esper in nature. Other than that I would expect some demons but no Zombies or Vampires.
Saheeli is a given for the Plane since we have her key art, though I fail to see her being UR. The stories we have of the plan seem to indicate that the authorities there are UW and she seems to represent the Authorities, so I wouldn't have it out of the question that she is UW.
Chandra is a probable as we need at least one of the Gatewatch there, so she will be Mono-red.
Tezzeret is a good call as being there, especially if Bolas is the one stirring up trouble there. Perhaps Bolas wants the Aether freed so he can gather it up himself!
That leaves a Green Planeswalker. I think that Wizzards has really struggled with good mono-G planeswalkers for some time and they had trouble finding a green planeswalker for Shadows over Innistrad. They had Garruk and he has become dark, leaving only Nissa as a Mono G planeswalker for the Multiverse. My prediction is that this will be a new Mono-G Planeswalker that comes to Kaladesh from outside to free the natural Aether on Kaladesh from its entrapment by the Authorities so that the Planes natural cycles can start again. This planeswalker unites with Chandra to form a rebellion against the Authorities that killed her parents.
No second white mythic. White really got the shaft in this set compared to the other colours. I'm sure there some other good white cards prior to Modern.
I don't see Tamiyo as either UR or UB. She's definitely not emotional or particularly inventive which rules out UR and she's not really that selfish either. The only splash colour I could see that works for her would be green since she has a desire to document but keep things the same. So if she was going to be multicolour in EMN I'd go with UG. However I'm going to stick to my assertion that she will be mono blue.
I'm saying now that Tamiyo will be in the next set. WoTC has had blocks before with two Planeswalkers of the same colour in them and I see no reason for her not to be in the set. Tamiyo is a major player in the storyline and the story ended with her about to explain why killing Avacyn was a really bad idea. I think she will hold the key for trying to solve things in the set and as such will almost definitely have a Planeswalker card. I feel that they can't bring her back in the story and not give her a card. Tamiyo has acted extremely mono blue in the story so far - she has only recorded things and not interfered in them, so I think she has to stay mono blue.
I'm hoping that she will do something cool like interact with a new subtype of cards like Instant - Story, but if I was a betting man I bet she makes clues as her +1.
What Tezzeret wants from amongst the inventions I'm not sure about, but it is most definitely not for the good of everyone and I suspect it will be something for Bolas.
It'll be a Pyramid scheme of course!
Saheeli Rai - RU
Dovin Baan - U
Nissa Revane - G
Chandra Nalaar - R
Liliana Vess - B
I'm guessing that we won't get a second Liliana card so close to Eldritch Moon and that she'll be in the background of the story but won't get a card. This means that we are missing a white and a black planeswalker in our list. Now we haven't yet seen the villain who is sabotaging things, so its probable that there will be another Planeswalker in Aether Revolt who is revealed to be responsible. The Gremlins in the past have been black aligned, so I'm guessing that the hidden villain will be black aligned who is stirring up the rebels.
I also wonder if both Chandra's parents really died twelve years ago. They have deliberately left things vague.
We 'know' that mechanic E is most probably the vehicle mechanic. I would expect perhaps one more artifact related mechanic. However I would expect that Green will have a mechanic that will not be artifact based but will be on the side of the rebels.
Also the mechanics are usually restricted to certain colours in the colour pie. I wonder if the mechanics in this set will be more based around enemy coloured pairs giving us:-
Red / Blue - Inventors
White /Black - Consuls
Red / White - Consul's forces
Blue / Green - shapers of the Aether
Green / Black - rebels
As to black. We haven't seen anything of black so far in Kaladesh. I wonder if the Consuls have a black component to them, making them Esper in nature. Other than that I would expect some demons but no Zombies or Vampires.
Chandra is a probable as we need at least one of the Gatewatch there, so she will be Mono-red.
Tezzeret is a good call as being there, especially if Bolas is the one stirring up trouble there. Perhaps Bolas wants the Aether freed so he can gather it up himself!
That leaves a Green Planeswalker. I think that Wizzards has really struggled with good mono-G planeswalkers for some time and they had trouble finding a green planeswalker for Shadows over Innistrad. They had Garruk and he has become dark, leaving only Nissa as a Mono G planeswalker for the Multiverse. My prediction is that this will be a new Mono-G Planeswalker that comes to Kaladesh from outside to free the natural Aether on Kaladesh from its entrapment by the Authorities so that the Planes natural cycles can start again. This planeswalker unites with Chandra to form a rebellion against the Authorities that killed her parents.
There - that's my crystal ball predictions!
I'm hoping that she will do something cool like interact with a new subtype of cards like Instant - Story, but if I was a betting man I bet she makes clues as her +1.