I love the first PREDATOR, and PREDATORS was Ok. Past the 2nd act, it gets sloppy I think but, even though I'm indifferent to the series, it seems like they have wasted a lot of opportunities to elaborate on the mythology of the monster.
What works most about PREDATOR is the idea that an alien species hunts humans. So, it seems logical that the expansion should somehow stick with that theme but also bring it together. PREDATORS varied it, but it didn't go anywhere. They spend too much time worrying about cool weapons and new armour and not enough on elaborating on the concept. If it continues from PREDATORS, the logical step to me would be to have Royce stow-away on a PREDATOR ship and get back to their homeworld, and then have conditions on that planet give humans an advantage over the PREDS in the hunt, and have him hunting some other less advanced race of Predators, so the roles are reversed and then maybe add Predators trying to hunt him down as well. Sort of like BLADE RUNNER meets PREDATOR on the PRED homeworld, with a twist, where human biology gives us an advantage, similar to the way the Pred tech gives the Pred an advantage on Earth-like environments.