Marvel Infinity would be EPIC! I would be in serious trouble financially if it ever occurred, but who needs money anyways. I also wouldn't mind Marvel Themed Variant Figures such as Mickey as Spider-man or Donald as Hulk.
FYI: Disney and Marvel's first crossover debuts this summer with Phineas and Ferb: Mission Marvel. It is going to be LEGEN-wait for it-DARY!, and this is coming from a 32 year old with two boys.
I have no doubt they will let the dust settle on how awesome Infinity is and when the numbers reflect a winding down after a while we will be teased with something regarding Marvel or Star Wars. They know exactly how those two franchises will boost interest and in turn sales. So it's just a matter of time.
There are some I like and some I don't. The odds are high, with the sheer number of Marvel characters, most of the ones will be the ones I don't want to see.
In general though, I'd have to say, including them isn't really a good idea.
There's enough Marvel games already that including them in this game isn't really necessary. Also, the sheer number of Marvel characters would outnumber the Disney ones 10 to 1. We'd essentially be converting the game into Marvel Infinity Online.
For the same reason, Star Wars shouldn't be included.
There was a Prep and Landing/Avengers crossover before I think. Also, I just thought of something. What if Howard the Duck came from the Ducktales universe? Anybody thought of that?