These modern sequels-but-not-sequels/remakes-but-not-quite of which Predators is the latest, are IMHO intended (at least by the studios) to be all things to all people. They try to avoid directly contradicting those previous movies that they know were successful, but they also talk a lot about 'reimagining', 'rebooting' etc, and plump for a title without a numeral - so that new audiences and fans looking for a fresh start can more easily forgive previous 'sins'.
It's a marketing technique. One that I'm fine with, but one nonetheless, and worth remembering to avoid getting too worked up about how the film's supposed to fit with the others. Let it fit wherever suits you - personally I love Predator and Predator 2, and unless there's a direct contradiction, this will fit with those. The AVPs I'll probably treat as separate entities for the most part. Some will embrace everything, others only Predator and Predators, and, shock-horror, some will never have seen any of them and Predators will be something totally new and stand-alone.