All long time Resident Evil fans know that, Wesker infected himself with the Prototype virus during the Mansion Incident in '98. Though, Jake has the appearance of a man in his late 20s as opposed to being a teenager, suggested by the given time frame. Though this is obvious to everyone. But it might be possible that Wesker knew about Jake's existance and infected him with the virus, (in hopes that he would continue his legacy) but kept it a secret in fear that he might be captured by the BSAA one day. Could it be possible that he was lying when the Woman confronted him about his relation to Wesker. But then again who knows.
Another thing I find hard to believe is that Wesker was able to some'what reject Excella's advances ( I know some ppl like my friend think she' s ugly but I think she's beauitful.) I guess I'm trying to say that I hope Jake's mother is Wesker's type; in the first novel (though not canon) Wesker states that he likes smart pretty blonde women, and hope Jake's mom matches that otherwise it'll seem too out of Wesker's character.
In all I feel that Jake's character was CAPCOM's way of compensating for Wesker's death. In other words it was their way of saying "Sorry we killed Wesker, but he'll live on forever through his son Jake."
Anyways I just want to know your thoughts :)