There is no "exit" strategy for Putin.

I believe Putin will end up being killed by someone close to him. He can't retire in peace; he has to many enemies inside and outside of Russia.

Putin has gored the Russian bear. Long before the war in Ukraine, Russia's birth/death ration was alarmingly bad. Now he has sacrificed the most productive demographic of his country. Russia is in rapid decline and its only hope is to seek peace before things collapse, but Putin is unlikely to be part of that effort.

The end will likely come sooner than later.

In spite of this war, Russia's future as an independent state is more dependent than ever on joining Europe. That will require pretty dramatic political change in Russia, change that Putin won't be part of.