A man with a private army on campaign is clashing with ineffective and humiliated political leadership back home, while trying to win popular support? When does he cross the Rubicon?
In another sense - he's a minor warlord, with ~50,000 armed followers, in a huge country. He controls ~zero of the infrastructure, air forces, etc. which would be needed for him to mount even an obviously-doomed bid to topple Putin.