Alzrius
The EN World kitten
Insofar as those go, I don't see #1 as being a major problem. The point of having the last book be the one that's opened up is that the author has already made a profit off the series, and so isn't undermining their own source of funding while simultaneously allowing for other people to play in the world they're done with. If it turns out that they're not completely done with the world, I'm not sure how another book from them would negatively impact anyone (even themselves, since "official" materials would still fetch a premium).
Concerning point #2...I can't really speak to contract or IP law, but I doubt that this would be an insurmountable barrier. The biggest hurdle would likely be the fears that derivative authors would claim that elements from their works had been used in licensed productions without their input, but that doesn't seem like it'd be a major disincentive if the series was popular enough to be made into a major motion picture to begin with (since those sorts of claims get filed anyway; this would make them a bit harder to fight off, but I don't think they'd be a deal-breaker).
