That rumor was always nonsense. There was never a chance that Capcom was going to rebrand the completely dead Infinite as MvC4.
What I believe they'll do is a true MvC4 that is marketed as the "true" sequel to 3 and a return to form. An improved art style and 3v3 will be selling points alongside the return of X-Men characters to the roster. Book it.
This thread got me thinking... have any other movie trailers come out without even revealing the title of the movie? The only one I can think of is the first Cloverfield trailer. (Damn that was hype at the time.)