If Amazon is to be believed, Archie Comics are set to collect the complete Sonic and Mega Man crossover, Worlds Collide, in a single hardback volume. "Sonic/Mega Man Worlds Collide: Deluxe Edition" is a 336-page book due on November 25th, 2014 for $46.76 US. That's just about enough pages to collect all three individual Worlds Collide trade paperbacks!
Further, Amazon lists a limited edition version for $73.54 US. Pending official word from Archie, however, we can only speculate what makes this so "limited." Foil dust jacket? Additional pages of concept art? Who knows.
So if you've been meaning to check out the crossover, this may be the way to go. More news as it comes.