I was actually thinking about this recently too. I'm pretty sure though that legally they wouldn't be able to do this. Although Lucasfilm owns the rights to the movies they wouldn't have the right to release any fan edit without permission from the creator or monetary compensation. A high-end fan edit would have had a lot of work done to it,whether it be editing, sound or FX work so Lucasfilm would have to pay the relevant fees for the work undertaken before they had a chance to do this. On the other hand this wouldn't necessarily stop Lucasfilm recreating any fan edit with their own company resources and releasing it as their own and maybe just put a small credit somewhere if at all.