the similarly hugely budgeted Golden Compass bombed the shit outta Murica and utterly killed it internationally, the sequels could have been made cheaper too as the tech they needed was already built, we never did get another one, did we? That same story happens all the time.
Pacific Rim looks pretty good next to actual bombs like White House Down, The Lone Ranger, and R.I.P.D, but just because it didn't shit the bed entirely (it still don't look great, and best case scenario it looks okay) doesn't mean people are going to rush to make a sequel, or give Del Toro another mega-budget to play with. Of course I think I'm just parroting Oscar here, but the man has called it pretty well.