..how does Pacific Rim compare to Transformers?
Either way, what should be reminded of, is the fact that Pacific Rim is dealing with the mecha genre. Truthfully, they wouldn't need to be expanding the armory currently from T2.
The only two IPs that have that (which have been rumored for the replacement) is Bourne, or the 007 series.
Sincerely, those should be what is most likely. Not Pitch Perfect, not Pacific Rim, not Jurassic Park, and not Sing. It's one of those two, and considering the odds of Annapurna making the next Bond film and not Universal, it's most likely going to be Bourne.