I have vehicles basically in 3 categories, at least by my personal standards, at this point...
-Definitely doable... Tatooine Skiff, the Speederbike, AT-ST, Snowspeeder... This stuff is largely done. The skiff's about the only thing left I can think they would do from the OT that they'd upsize and improve upon. The only problem is the originals aren't even all that hot sellers, so how is the new one gonna do? There's some little stuff that could sneak in like the Hoth Sled, or the deleted scene Hoth Repulsor Tank, but not much else it seems is left... EU stuff doesn't count IMO.
I would throw a vote to the ANH:SE Swoop though... And the Tatooine speeders, but the Lars Speeder etc., are pretty obscure. I'm not counting on these ever happening.
But the Swoop... yeah, I'm all for that. New rider with a pointy hat too. It's technically never been done, as the SOTE one isn't in the ballpark of what the one in the movie ultimately looked like.
I'd also dig a "variant" AT-ST... Take the current mold, make a couple changes like to the legs and things. I'd take the Hoth version if they resold it and made it a bit more accurate to the model. Not counting on it again, but yeah.
-Doable, But Costly... This is X-Wing, Vader's TIE, Y-Wing... I'm ok with Vader's TIE as-is, it's fixable, but I'd take a new one for sure, if offered, and a vast improvement. The Y-Wing and X-Wing are both doable though, but I want these to-scale... I favor the X-Wing though because it's trully iconic. I like the Y-Wing though, and would love to have one I'm proud to display, as it's currently the weaker of the two... That said, it's also less iconic. I'd put a B-Wing in here as well. A tad larger, but mostly due to the longer body which is thin. I'd take a new one though, but it's lower on the rungs for me. XW and YW are tops and would really need to be special.
The CW Y-Wing is really pretty much what I'd want, in a new OT Y-Wing. It's almost perfectly sized (short by like an inch or two), features the stuff I want like the droids socket, and the 3 landing struts, and a sizable cockpit... It's funny the cartoon y-Wing was drawn basically too big, to have been the OT Y-Wing stripped down, despite that being the intent. Regardless though, YW would be high on my list right behind the XW, and I feel Hasbro can and should do both.
Can't think of anything off-hand they haven't done already, in one shape or form.
-Doable, but not to-scale... These are things more like playsets, and less like a vehicle you could feasibly pick up and run with if you were a kid. Queen's ship, Slave-I, etc. It'll never happen to-scale, not from this company, and even if it did a lot of people would be scratching their heads where to put it. I put the Sailbarge in this category.
Via twitter I've read Frank D'Iorio (Niub Niub) is doing (currently) a scale Sailbarge for his diorama workshop at C6... I'd imagine he'll be posting plans on his site for it. I think I may make one as that'll be a fairly simple way to do it. I really want one for some reason, and even if Hasbro does this, it'll obviously be smaller than it should be. I think I wanna replace my Jabba Palace shelf with a Sailbarge though. Just seemsl ike a cooler display.
Lots of things could fit this bill... Scale Falcon, Scale whatever... Hasbro wouldn't ever do most of them. They'd maybe only consider others, and they'd be smaller thingsl ike Slave-I. I'll work on these on my own, someday, and just be happy for the folks who want them if they ever get things like a repaint of the new Slave-I mold and whatnot. I think the demand is there and warranted to make it. I think they've had every intent to do so since they made that new mold though, considering the features they built in. Just a matter of finding a home for it, as they say.