Well it's Capcom, they revive characters like nothing, but in the Comicon Resident Evil's producer was quite enfatic to say that Wesker is not comming back except for precuels.
"Even if you want Albert Wesker to come back," Kawata told the crowd, "there's no chance he's coming back from that.
http://wii.ign.com/articles/100/1006934p1.html