That is a possible move. An attempt to cut off the Baltic States from Poland and to reunite Russia, through Belarus, with Kaliningrad. He might also invade Latvia to provide a direct route uniting Russia to Kaliningrad, where it has its Baltic Fleet.
He's definitely thick enough to try it. And I'm sure he has reserves set aside for it. I think he assumed he could roll Ukraine easily to begin with and then he would move against the Baltic states next.
But now... well, NATO will wipe his army out if he tries something like that. And I don't doubt we will annex Kaliningrad if it happens.