Looking at the official Marvel announcement of their inevitable 2014 Comic-Con panel, it's about as vague an announcement as possible. The "when" is Saturday, July 26, from 5:30 to 6:30 PM. The "where" is Hall H. It's just the "what" that they left very, very loose.
Marvel's pretty much taken up permanent occupation of that spot, and why not? It's the last big movie panel of each year, and being in that position means that they have a chance to throw down something big and buzzworthy and basically dominate the conversation as all the movie coverage is wrapping up. It's a brilliant strategy, and I'm sure they've got some big things planned for this year.