While Guillermo Del Toro has always pushed for a Pacific Rim sequel, the likelihood of it happening was slim at first. The film had awesome giant robots battling equally massive kaiju, which for some reason didn't make much of an impact here in the States. The rest of the world loved it, and the $200M movie ended up with $400M when all was said and done. So the sequel, Pacific Rim: Uprising became a reality, minus Del Toro, and also without its biggest star at the time, Charlie Hunnam.
There was some interest in having Hunnam reprise his role as Jaeger pilot Raleigh Becket, but it never really seemed close to happening. In a conversation with Den of Geek while on tour for The Lost City of Z, Hunnam said the reason he couldn't do Pacific Rim 2 was scheduling, not because of any creative conflicts.
“There was a huge scheduling conflict. I was already really, really invested in doing Papillion.”
“What happened was Legendary (Entertainment, the production company behind Pacific Rim) was sold to Wanda, which is the big Chinese corporation, and Pacific Rim, although it underperformed in other territories in the world, was an enormous success in China. All of a sudden, it became their primary focus to make this and they wanted to do it very, very rapidly… I think their schedule subsequently changed, and I might have been able to do both, but at that time, they were writing the script and they needed to know, was I in or was I out?”
Hunnam was actually bound contractually to return for another Pacific Rim, but Legendary's Thomas Tull was kind enough to let his friend out of the deal.
“He was like, ‘Dude, you were going to do that other film and that's where your heart is. I don't want you being on set if you're not going to be happy, so go do the other film,’ which was ludicrously generous of him. But that's just the type of man he is.”
Pacific Rim: Uprising, which opens February 23rd 2018, now has John Boyega and Scott Eastwood leading the charge, with Rinko Kikuchi, Burn Gorman, and Charlie Day back from the first movie. So, let's say this one is a hit, there's always the possibility Hunnam could come back later. It's not as if there's bad blood.