Ryan has been pretty much on the way out since the first season. Why stay where you aren't wanted if someone else wants you to fill a need. Good for Ryno.
It's not a re-negotiation. He'll still get paid the full amount if they don't cut him his final year. I think.
It's significant but not as big as it looks. He didn't change his salary... he changed the guaranteed portion of that salary. For him to only get that amount, he would become a free agent in a year. In essence, he agreed to buyout terms. His thinking is likely I'll go somewhere that I'll play, then choose my own destination next summer (and get a salary). He likely only gave up a small amount and that was worth it to him to be able to play then choose the ideal spot for him.
He didn't renegotiate salary. They are allowed to renegotiate Compensation Guarantees, though, like we did with Lawson. Little known fact: The Uniform Player Contract is non-guaranteed. You negotiate "Lack of Skill" percentage compensation into it -- like 100% of Base Salary is guaranteed. That amount of compensation that is guaranteed can be redefined.