NewGame+ and Transmog are by far the things I want most, so much so that I'm starting to resent the game for not having them lol.
Pallys picking a deity would be cool.
Crossplatform would also be neat.
There's also some class changes I fantasize about even though I know they'll never happens;
Like War Caster on Eldritch Knights adding their Str/Dex 2x to their cantrips, or Weapon Bond acting like pact weapon...
but mostly just NewGame+ and Transmog
