No. Bringing Wesker back now would be just silly, pointless... I don't mind older characters returning to new games, as long as they have a reason for it. Fanservice just for the sake of fanservice generally ruins a story, not to mention that most RE characters are so overused now, especially Chris, Jill and Leon - it's time to stop using them and Wesker is no exception, his story is pretty much done for good. Wouldn't you be bored if Wesker showed up again? Heck, as Hel said, he never was that good of a villain in the first place, and the opportunity Capcom had to add more depth or development to his character (RE5) was completely wasted. Either way, that boring Chris-Jill-Wesker rivalry/arc was finished in RE5, I see no point in bringing that back now.
And regarding the "RE's story was always ridiculous" thing said here, I disagree. Yeah, RE's story was never breathtaking, but RE1, RE2 and RECV stories aren't that bad compared to the stories of the most recent titles of the series IF you consider that those games were made in the 90's. Of course, many themes and dialogues from those games are cliched or cheesy now, but they were decent enough at the time they were released. The relationships between some characters (RE2!Claire-Sherry, RE2!Leon-Ada, RECV!Claire-Chris, RECV!Claire-Steve) were overall more deep or interesting than the interactions we see in RE5 or RE6.
As for RE6 not establishing anything new to the future of the series, I also disagree. I really don't know what they plan to do with this Ada/Leon relationship that is never concretized, but Chris was pretty much humiliated in RE6. He acted like an angered child for the most part of the game, almost his whole team died because of his incompetence and at the end, Piers - the person he trusted to take his role as captain (he even mentioned he was planning to retire) - sacrificed himself to save him. If you pay attention, all the other campaigns had a "happy ending", but not Chris' campaign. Capcom probably plans to develop his character or change the way he faces bioterrorism, given his personal failures and hero complex.
RE6 also presented Sherry and Jake as new characters, which was a breath of fresh air to me. Their relationship is somewhat interesting, since they are the only people in the world with special virus immunities and all. I think Jake hasn't overcomed the fact that he is Wesker's son, and you can say the guy has deep-rooted trust issues. All in all, Jake's character development could be further explored in the next games.