I too caught the Narset hint. We know she's been there at the very least and may show up.
Just reading the PW guide and I'm already annoyed by Vivien. Like, does she even eat meat and use animal byproducts? The most obvious reason for monster hunting in my opinion would be for food, animal byproducts and domestication and none of these seem unwarrented in a world where human survival is so grossly threatened. I originally like Vivien when we first saw her blurb but after reading stories associated with the planeswalker, I'm starting to think I'm ot as G as I once thought. I think I might even get the Human-tribal edh deck. I'm a huge human tribal fan and was previously in the midst of building a Samut-led deck with that theme.
Other Planeswalkers I could imagine being featured on Ikoria if Narset isn't carded is Huatli (Dinosaurs)and of course Kiora.
I like Luca from what info we have on him. His source of conflict is relatable, he cares about humans and monsters, hell his story even has a romantic subplot.
According to Maro, Humans and possibly Human tribal will have some import in/on Ikoria. This new information brings to mind a fact that we already knew, that despite Ikoria's design being mostly bottom-up, some of the set's design will be top-down. I predict, as many already have, that the human-centric elements of Ikoria will represent human civilizations responding to Kaiju monstrosities in a vein, not unlike that of Innistrad; working together to use magic, systems and technology to protect themselves. These elements would fit top-down tropes related to Kaiju movies and related fiction.
Normally I'm not a big fan of artefacts but I strangely found myself actually enjoying the look of the mechs in Kaledesh. I think it would be appropriate and fine were they to appear in Ikoria so long as the flavour and the art strongly convey that these are artifacts powered by magic and possibly powering magic in return.
Of the commander decks that I could see being more human-centric, I could see Ruthless Regiment, Arcane Maelstrom, or Timeless wisdom being somewhat human-tribal.
Ruthless Regiment could be so because it represents Human militia and armies that use centralized social systems to protect the state and society. RWB or UBW
Arcane Maelstrom might not be human-centric, but I could see it being Wizard-tribal; representing Humanity's mastery over magic in order to defend themselves. URW I cannot think of another three-colour combo that would better fit this.
Timeless Wisdom could also be human- or spell-centric if it's UW but if it's GUR as many suspect I could see this not being very human-related at all.
In the meantime, if anyone familiar with both and the source material has any ideas of what tropes, narratives and monsters we could expect, I'd greatly appreciate hearing it!