What I gathered from Q&A's over the last year or so implied to me that vehicles were costly and didn't always move well but Hasbro's used the "repaint and rerelease" formula like with figures to get out new vehicles periodically... I guess things like the Sith Infiltrator wouldn't have made it to retail without umpteen Jedi Fighter re-releases, etc. Basically the figure formula is working on a smaller scale with vehicles...
On the "big vehicles" front though, we reported a story a while back that the major/ultimate reason Hasbro took the big leap on those was due to the sales rates of other large toys last holiday season. In particular a creepy animatronic pony that did phenomenally well, and surprised them. Coupled with the CW release/push then the notion of some big SW vehicles for big prices seemed like a pretty great idea, and here we are... I think their messages of "if these do well... " have been pretty true then. If the Falcon or TE do well, they'll strongly consider other larger items. If they don't, they won't.