Oh, they could have released a playset and some vehicles before, all right. Of course, that's IF they would have put a little more faith, ambition and investment into this line ! I mean, come on, MOTUC was initially a 6 action figures plan ! That tells you about Mattel's short-sight for MOTUC.
They were scared to relaunch a MOTU line after the 200x demise (a 20x demise that was due to THEIR marketing habits : bad case ratios, too many variants and repaints, availability problems... all due to a "cutting costs policy"). That's why they didn't plan any vehicle or playset before.
The big difference, these days, is that people at Mattel are chilly to invest. Why ? It's not only due to the state of economy (other companies are not so chilly and show more faith and ambition). It's also due to one of Mattel's main policies since the beginning of the 21st century : cutting the costs. THIS is really what caused the 200x demise, and this might be a problem with MOTUC too (and it is also a problem with other Mattel brands such as DCUC, for instance).
Basically, you say "trust Mattel and the way they handle their business". Well, that's what I did with ALL the MOTU properties in the past. And guess what ? I always regretted it and felt betrayed after the end of those toy collections, because the different lines always stopped abruptly, leaving a bitter "incomplete" feeling and taste in my mouth.