It would be fun to see a 'Disney TV Animation' playset that you could use a variety of characters in. Scrooge, Darkwing, Goofy, Chip and Dale, Mabel and Dipper, the redhead spy girl (i forgot her name), etc. They could just make it be a big crossovery melting pot and throw whoever in.
Alternately they could do a Toontown set and let you use Mickey, Minnie, Donald, Goofy, Scrooge Mcduck, Chip and Dale, Darkwing, etc who all fit into that same 'universe' in it. There's plenty of characters who can hook into a Classic Disney sort of setting even if some of them get a little weirder (like Darkwing).
I really want to see Chip and Dale as one figure though. Which sounds weird probably, but it makes a lot more sense to me than splitting them up. And you could have a Rescue Ranger costume disc for them.
As for Star Wars: I disagree that R2-D2 wouldn't be viable as a figure. He has extendable arms that can hold things or swing weapons, he has the jet boosters that let him jump or fly, he has his shock prod thing and his oil spray. They could make him work as a figure with really fun combat and I think he'd be a strong seller. C-3PO though, no. He can't really do anything. He'd be fun as like a cosmetic follower or something though for R2.
When it comes to Marvel, I think the rumored four seems likely. Ant-Man, Scarlet Witch, Quicksilver, and Vision? Yeah. I bet Scarlet Witch and Vision are packed with the new Marvel Battlegrounds set (they like doing one guy and one girl for those). Personally I'd like to see another Spider-Man villain like Doctor Octopus, or some more comic book characters like Wasp or Captain Marvel. But I imagine a lot of these are going to wait for them to appear in the movies properly and release then. I bet 4.0 or 5.0 brings a lot of cool new stuff for Marvel but this one's going to be relatively low-key overall.
You can tell it's going to be a slow year for Marvel when one of the figures is a Spider-Man recolor using his existing power disc costume. It's not even like the Crystal figures where they're using new assets in some way. That's okay though, Star Wars needs the focus for it's first outing.