May seem silly, but its a small idea for new cosmetic items, some I would seriously consider buying so I may have a dapper outfit. So, a tophat and a suit would be nice.
As for the other suggestion, I dont know if this was suggested before so sorry if it is beimg repeated.
So, I think that in the future, actual living NPCs would be nice.
Things like merchants, blacksmiths, bakers, traveling merchants, brigands and quest givers. Maybe there could be new towns, made for these NPCs to live in.
Also with quests, the game could perhaps have an optional storyline you could follow, with maybe some villlain deep in the underworld and such. I am sure the community would help write up this story.