99% of lawyers will NEVER advise going to court. You almost always want the issue settled between parties before it gets to that point.
Now the issue that is bigger here IMO is whether the Thomas Bros. are entitled to the "Predator" design that Stan Winston Studios created for the film. Did he sign over ownership of the character to 20th Century Fox?
As others have mentioned, simply getting the rights back to "Hunter" about a alien space hunter is pretty generic compared to the ICONIC "Predator" Winston designed and created.
Also, I'm not down on the Thomas Bros. at all for trying to get their property back or pursue the copyright laws that may lead them to a better "pay day". Let's face it, Fox and now Disney have a very valuable I.P. in Predator and I think it's safe to say that none of us would have predicted the Predator franchise is as popular as it was back in 87. Video games, toys, t-shirts, cups, posters, etc.
Disney MILKS their I.P.s dry and are making literally millions upon millions of dollars from all the intellectual properties they own. The Thomas Brothers have a legal right to re-capture those rights. There is *NOTHING* wrong with that.
I'm still very hesitant with Disney owning the ALIEN I.P. and have no idea how that it going to go.
Anyways, I still think best case scenario for all involved(fans, Disney, Thomas Brothers, production staff on Skulls) is that a settlement is hammered out that is amicable to all sides.