Well it's confirmed that we're going back to Kamigawa next year- sort of. Gone is the feudal era, replaced by something that looks like Neo-Tokoyo. Perhaps it will draw a wider audience, and some of the traditional Japanese lore was sort of inaccessible for the average westerner.
Legend Mechanic- something like grandeur seems possible. While the set will possibly have a lot of legends, it seems like something that needs support.
Tribal- Kamigawa had several unique tribes and classes.
Snakes could come back as G/U. perhaps they'd get a piece of the ninja pie. something more than more +1/+1 counters. Green is sort of suposed to be the master of combat tricks, anyway.
Kitsune- I think they might have a k-pop theme this time. not sure about actual mechanics
Nezumi- Probably back as Yakuza gangsters. Perhaps the Oni are the bosses.
Samurai- Since it's not the feudal era anymore, they're probably gone.
Shrines- Perhaps they could be tribal shrines, that care about thier tribes rather than other shrines for instance
Ninja Dojo- 3B
At the beginning of your upkeep, target opponent loses x life, where x is the number of ninjas you control
Pretty sure it's common in the cyberpunk genre to refer to the warrior/soldier archetype as "samurai". It may not mean exactly the same thing it used to, but anything from corporate private soldiers to ronin mercenaries could fit the creature type. Now Bushido, that's probably gone, both mechanics and lore-wise.