Well, Westbrook could stay with the Lakers, but what if the Lakers will decide to trade him? He has no choice but to accept his faith because whether he likes it or not, it's very evident that he is not helping the Lakers achieve their goal to win a championship again.
Saw some article rumor just recently that it's likely that Westbrook will be traded to Spurs while Kyrie to replace him in Lakers.
It seems that you're saying is really possible to happen but until it's official and there's not yet actual statement, it should remain as a rumor. But yeah, it's very likely that he'll be traded if the Lakers decides.
There really is nothing he can do if he'll be traded then.