Okay, if Hasbro can make the MMT, they can surely make a Sandcrawler...
...or Jabba's Sail Barge.
The MMT, while kind of cool, is basically a big, brown lump. A large Sandcrawler or Jabba's Barge would look much the same when it was all closed, but both would have lots of cool play opportunities with opening panels, etc. like the MMT seems to.
Maybe we'll be treated to big versions of those when ANH and ROTJ make it to the theaters in 3D.
If the MTT sells okay (which, at $140 SRP seems like it might be a stretch) and TPM 3D does well enough to justify the others coming out in 3D...I think you can probably count on one big new vehicle for each movie.
For Clones, not sure what's left. Maybe a full-size Dooku solar sailer, or a more to-scale gunship with gunner pods.
Sith - maybe Palpatine's shuttle to Mustafar.
ANH = Sandcrawler seems obvious.
ESB - no idea. They've done almost everything. Unless they want to try and do some kind of Star Destroyer playset.
Jedi - Sail barge is the obvious choice.
For an RotJ set, I'd much prefer an Ewok Village than Jabba's Sail Barge.
I agree with most of your thoughts, although for Clones I would really like to see Amidala's ship from early in the film. Not the decoy fighter she was actually flying, but the larger chrome ship that had a 1940s or 1950s look to it.
For Empire, I imagine them just rereleasing the AT-AT, but I also wonder if they wouldn't go the retro route and create either a large Hoth or Dagobah playset, the latter including Yoda's hut with a larger, more detailed and more accessible interior, as well as a more expansive "yard." 
There's always the medical frigate from the very end of the movie, too.
I don't see the MMT selling at all at full price. It's going to be one of those giant boxes that clogs up the aisle until Christmas when it's clearanced out at 75% off.
The problem with the Sandcrawler is that it could be perceived as a boring toy. It doesn't have any weapons. It doesn't belong to the heroes or the villains. It belongs to hooded junk dealers. I remember the last time Hasbro released the Sandcrawler, Target turned it down as an exclusive which is why it ended up at Tower and Hot Topic.
I am biased because if we do get a big vehicle from ANH I want it to be the Tantive IV.
Yeah, I think that's also the logic as to why we don't really get playsets - toy company research seems to show kids want action vehicles that can do battle, rather than static environments or non-combat ships.
With playmates doing that huge Sewer lair for TMNT, though, I'm wondering if the conventional wisdom on playsets is changing.
But on the other hand, how hard would it be to add some sort of hidden pop-out cannons to a Sandcrawler, like the escape pod on the BMF?
Seems like it'd be fair game unless Lucasfilm objected that it's too non-canonical.
I think it would be better if they went the "Droid Factory" route with it. Make it more like a playset with tons of pull-apart and make-your-own droids. In the movie, that room that R2 and 3PO wound up in inside the crawler was full of junky robots. That could be kind of fun, and would tie into any build-a-droid stuff they've already put out.
Was thinking the exact same thing. If Hasbro can release a large, probably expensive, vehicle whose sole play value is nothing more than ferrying droids on garment racks, while ignoring the obvious play value in a mobile droid factory then someone needs a demotion.
Yes, the MTT does tie into EP 1 (IN 3D, NOW IN THEATERZZzzzzz...YAWN!) but other than electronic sounds, and a motorized unloading feature it is a boring toy. The play pattern is passive, whereas a sandcrawler with various mix & match droid parts would better engage a child, and would make most classic collectors (with the $cratch) happy as well.
...and if you throw in any missing droid( s ) from EP IV, that's just gravy.
Mr. Tibbs