Matthew McCallum wrote:
Indeed, the MPC line itself has started collected some series in advance of Masterworks such as Black Widow, Guardians Of The Galaxy, West Coast Avengers, and Moon Knight. And we know from Cory that the Black Widow MPC scotched his plans for a Black Widow / Doctor Doom / The Watcher Masterwork volume.

I think you're right about this.  The Classics lines (e.g. Champions, New Mutants, What If) also seem unlikely to be Masterworked in the near future.  I'm kind of hoping they'll make an exception for Tomb of Dracula, though.  So far I have generally avoided omni's because of the perceived unwieldiness of the format, otherwise I would have picked this up long ago.