Okay so Gates to Infinity was... Bad? But this new one looks really cool from what's been released so far, so I'm just going to go ahead and show what we know so far:

There are now 20 starters - all the Region starters with Riolu and Pikachu. Furthermore, many websites report still no personality test but I can't find this on the official site (but maybe I'm not looking hard enough haha :') )

The cutscenes are more fluid now, although I guess this is expected with the jump to 3D, but for anyone who hasn't seen the trailer I would suggest watching it
here, the Entei and Kyogre bits particularly seemed cool!

Lava is back, I'm pretty sure it wasn't in Gates to Infinity but I may be misremembering, but if so then just admire how beautiful the lava is haha xD

The story is about Pokémon being turned to stone (and Lombres back?), with Arceus confirmed to be in the game and given stone Arceus in Destiny Tower (EotS) it wouldn't surprise me if he were pivotal to the story.

This doesn't confirm anything other than Rayquaza and Deoxys, but it looks very Delta Episode-y to me? Seems odd but idk.
Then there's a few things I've found reported confirmed but can't find:
-> Aforementioned lack of personality test
-> Hunger mechanic returning
-> Monster houses
To date there has been
no confirmation of Mega Evolution.
So yeah, that's everything we know so far I think, looks like it could be pretty good with the return of hunger and less limited amount of Pokémon by the looks of it ^^
Edit: whoops just saw a similar topic in Games General >_> Can't delete this so I'll just leave it but yeah sorry xD