No, he will stay for 2 years as that's what his contract says.
If he cannot make it next season, he still has one more season to help the Clippers win a championship. I think it's possible as long as Leonard stays healthy. Actually, even without PG, Leonard and Westbrook would already be enough to lead the team.
As compare to let's say Oladipo or Dennis Schröder by declining a huge contract and then later on signing for lesser money. But in this case, WB is on the opposite end of the spectrum and it could paid off.
Westbrook can receive a lower salary as he already made a lot of money during his time with OKC. On the other hand, in the cases of Oladipo and Dennis Schröder, they were at their best when the contract was offered, but they gambled and got a bit greedy, looking for bigger offers. Unfortunately, it didn't happen, and for sure, they regretted that decision.
Yes, Westbrook's net worth is already $200 million, according to Celebrity Net Worth: https://www.celebritynetworth.com/richest-athletes/nba/russell-westbrook-net-worth/
So he can take a lower salary because he already has a lot to fall back on. The Clippers did not have to make a difficult decision on what they could offer Westbrook, as he willingly accepted a very low salary. Just imagine, that's only more than 10% of his yearly salary during his prime.
He probably just want to solidify his achievement because as an individual player, he already made a history, so winning a championship will make it better.