The rockets at the end missed and the lava did not seem be doing mouch damage to wesker. However it is highy unlikely that he survied that last battle. Wesker was blown to bits by twin RPG's in the face. I highly doubt that he could survive such a death. Even if he is truly dead, at least he died in resident evil style`!~
I think that another one of the Wesker children survived and that would bring back good old Albert Wesker but this is only my thoery because Wesker never dies!!!
It is also important to notice that Wesker was shot with a RPG by Chris before so Chris could inject him with the serum. When he was shot then he was only stunned temporarily, about 10 to 20 seconds at most.