Russia Ukraine war, page-4376

according to former oligarch who fell out with Putin, Kremlin critic Mikhail Khodorkovsky.

It's distracting with 2 languages involved being then translated into English but worth a close look.
He sets out what he thinks the options are for Putin. This guy is a former insider and he seems to have a solid picture of the dynamics involved.
It's worth noting that the Kremlin structures that used to enable a leader to be removed, have been dismantled by Putin. He's so entrenched that it's difficult to see him being quietly removed or going voluntarily.
This leads to a further possibility: sustained uprisings over time.