Personally i really want someone to make a cross between Second Life with some form of actual game. Like Second Life crossed with an MMO or game like Skyrim - cept multiplayer. But in a more.. combat/quest optional way...
i dunno... a lot of times when i play MMOs i /wish/ there was more integration of what Second Life is too. Then i'd, personally, hang out in an MMO more. If there was more customisation of the avatar. More... potential ability for players to 'own' a home in the game and decorate it. Maybe somehow segregate the home zones in such a way that they are more sandboxy, but you are able to cross over, into the game when you want.. and still look as neat as you can in SL
i dunno! there was a MMO-ish thing in Second Life for awhile, Darklife, that me and a friend played.. but.. since SL isn't really "built" on a gaming foundation it wasn't really great... but i dunno!
for me.. that would be the thing to pull me fully out of SL. a true game-meets-SL sort of place.