The only reasons I don't think Baby May/Spider-girl will ever be brought into the main stream is because a) she is a piece of the Clone Saga, which Marvel seems to want as charred and buried as the clone that was in the smoke stack.
B) They use Spider-man as their cashcow, sadly enough, so deterring attention from him wouldn't give them what they want. Makes me think of Arana, though she isn't a direct Spider-girl, she has seen less success I believe than Spider-girl is said to have had.
C) The bas taste that Spider-man's marriage seems to have to JQ, giving him a child would push further down that family line, and again derail Marvel's bottom line.
I love Spider-girl, but as many times as they've wanted to pull the plug on her series, I think Marvel wants to wash their hands of her completely. It's a dissapointment in my opinion.