The producer did comment on it. From dnaindia.com:
According to producer John Davis, Arnold Schwarzenegger did not sign to act in Predator 2 because of a $250,000 dispute.
"The sequel to the first one rebooted it. We should've had Arnold in the movie. The deal broke down over $250,000, which is a shame. But it was moved from the jungle to the city. You have to create a freshness about it," Contactmusic quoted him as saying.
Even there were plans about how to use Arnold in the sequel:
The original plan for Predator 2 was for Arnold Schwarzenegger to return, using salvaged Predator tech from the first movie to continue the good fight. However, Schwarzenegger didn't want to come back, so the writers had to scramble for a new idea. - Cinema Blend
Arnold even openly slammed all the sequels:
"The sad story is that sometimes studios do a great job with creating
sequels, and sometimes they really screw it up bad, and it all has to
do with greed," Schwarzenegger said. "They sometimes want to do it
really cheap and make as much money as possible, so they don't hire
the right cast or the right director. ... It's stupid moves to make."
"So far, no Predator, no matter which one they did after the first one
has come out, has been satisfactory to the audience," the star
continued. - hollywoodreporter
He even spoke to Yahoo about the future sequel's involvement in a negative way in 2017:
My all-time favorite film of yours is Predator, and Shane Black is now rebooting the franchise with The Predator. Are you involved with it in any way?
They asked me, and I read it, and I didn’t like it — whatever they offered. So I’m not going to do that, no. Except if there’s a chance that they rewrite it, or make it a more significant role. But the way it is now, no, I won’t do that.
