I reckon theres a good chance that Wesker survived it, afterall if you watch closely the rockets fly past him and explode behind him, it wouldnt be the first time for a lava bath survival (Mr X in Re2 for instance)
But if Wesker is truly dead, I reckon there will be another Wesker, mainly because its the first time we have ever heard mention of the "Wesker Children" chances are despite what Spencer says about Albert being the only "Wesker Child to survive" it contradicts it in Weskers file going on about how there were a few survivors including Albert.
So there is a high chance of the "Wesker Children" playing a large roll in the next title.