I don;t know if we would ever see such an event but Omega Red will soon be appearing in comics again very soon.
The Return of Omega Red.
Originally posted by Umbrax
Where did you hear about that outrider?
A crossover is just when a story is played out in more than one title. In the context that NeoQuest set he is talking about "Intercompany crossover" like Spider-Man/Superman.
Is Silver Surfer a bad guy? Not anymore, but he was a threat to planet Earth in his first appearance. This story is what the upcoming Fantastic Four movie is loosely based on. So in the movie, at least for the beginning of it, the Silver Surfer is the villain.
Right now in Ultimate Fantastic Four , Ultimate Silver Surfer is about to make his first "legitimate" appearance.
In the regular FF books Silver Surfer is also making appearances (Marvel does this sort of thing to coincide with the movies) where he fights the Black Panther.