It's a crazy long shot, but I guess I will take a stab.
95% they pull him back and don't even take calls because Darvish is their horse and on a crazy cheap contract.
3% they ask for a big minor league return and we pass
1% they let him go. It's stupid, but the Rangers are an absolute dumpster fire out of nowhere. It's possible they're trying to get out from money any way they can.
1% they ask for a mid-level prospect to start gutting their terrible team and we make a deal
With all that said, I'm not THAT surprised Walt wouldn't claim him. I'm way more surprised people in contention right now or people less stacked in pitching 2015-2016 didn't claim him.