There are a few options here:
1) Putin is saber rattling. Scaring people in to letting him have his way - The world let him invade Ukraine. Now, he's taking Syria with little to no opposition. Little saber rattling might let him get away with what he wants.
2) Putin is preparing for war. Regardless of who wins the next US election, they will be the most hated incument in US history and will not have the political capital to go to war. The EU is falling apart to infighting. China and Russia have been doing joint military maneuvers. They're ready and they suspect that if they just do a massive show of force, the world will back down.
- Maybe China dumps its dollars, causing a dollar collapse and breaking the US without a bullet being fired. Then, it takes Taiwan and perhaps Japan. Russia steamrolls eastern Europe, threatening nukes to anyone who fights them. Suddenly, the world has Russia and China on top instead of the US.
3) Some third thing I haven't thought of.
- Putin has kept power in the former Soviet Union longer than anyone else. He is cunning. He is sinisterly intelligent and he is ruthless. I can't outthink him and, chances are, neither can you. We don't know his end game.
Ultimately, it might happen. Or it might not. If it does, expect bad things ahead.