Bandai isn't sitting on the Star wars license though. Same with Kamen and other sentai shit (aren't they co-owners or producers with a lot of that?).
They're regularly releasing those figures, which shows the structure of their license.
No licensor is going to allow a company to just sit on a property forever, because license agreements not only require money to be exchanged for the license itself, but also royalities PER figure made.
If no figures are made, that's money "lost" by the licensor. Hence license agreements usually stating that a certain number MUST be sold or penalties are paid. Sometimes a company will just eat the losses and pay the penalty if they don't think they'll profit from producing and releasing the product.
This is why Bandai wouldn't just re-up again, because they already took the loss (if a prototype was made in the first place) and likely wrote it off. I don't know anything about Japanese tax laws, but i doubt they're far off from US ones when it comes to be able to declare a loss, especially since Bandai is a publically traded worldwide company.
Bandai is a major company and WB is a major company, so there's no way they'd ghetto-the-fuck-out a deal like you're describing, which is basically redneck handshake agreements who know nothing except how to build a latrine trench.
Plus, movie shit usually requires seperate licenses, hence master licenses being a (big expensive) thing.