Now that ASM: Ends of the Earth is a success, would Marvel be willing to use The Black Widow and Spider-Man in future team-up stories in Avenging Spider-Man or a possible Black Widow mini series?
I don't really think it has a lot of impact one way or the other. We've tried BLACK WIDOW projects and likely will again, but we've not yet found an approach that makes an ongoing book viable. And like any other character, she'll guest-star in the Spidey titles when there's an appropriate storyline, but fitting her in there isn't really a priority.
Imagine if she was feature as a guest crime fighting partner in ASM: Maximum Carnage instead of The Black Cat? Anyway, if the guy who is writing Winter Soldier wants to do a team-up story with Spider-Man x The Black Widow, he could write that potential story in the pages of Avenging Spider-Man.