I don't necessarily mean the setting but more like certain features from past games.
Like for instance; I would like to see a lot more content this time as not only is it concluding Desmond's story but most likely starting a whole new ancestral setting.
I would like to see features from the old games but changed in accessibility, like the hookblade to be optional.
I think it would also be kool if the game would have A LOT of references to Ezio and Altair.
Maybe an item like... The armour/blade of ezio.
And some features similar to the Codex pages, because i thought they were really interesting in providing a back story. Maybe codex pages revealing Ezio's enhancements to weaponry.
I would also like to see the impact Of ezio's leadership after the events of embers.
Personally i wouldn't mind if they scraped the assassin recruits next time around, and focused on developing the character more as he/she wont necessarily a Mentor.