Well the next Fallout game will use the same engine as Skyrim, just with a few changes. I highly doubt Bethesda would scrap the engine any time soon, it's held together with masking tape and hot glue sure, but it does work. There's no other engine that does their games as well as the one they've made (albeit bolted on to GameBryo).
Honestly, I can't wait to see what fallout will look like with skyrim's engine, i know story and gameplay are the first thing to worry about but I can only imagine the character creator and the new designs for mutants and the like. And of course the towns and weapons. Wonder if they'll do better with ghouls this time around?
I am worried about story line and if they'll mess up even more FO lore this time around and turn it into something its not.
My expectations:
I'll be fine/and very satisfied with graphics if they are on par with Skyrim.
Story and complex choices and the whole RPG she-bang is my biggest concern.
Gameplay - I think melee will be much improved, possibly speech as well(bribery please?), more interesting locations and characters of course. I think they'll satisfy me but I will probably want more.
My biggest worry is there emphasis on perks from Skyrim. The actual leveling of a skill hardly does anything. Perks dominate it all. I hope FO doesn't follow this and perks only add interesting small fun bonuses and are not chiefly needed in the game.