Based upon historical precedent, Putin expects the West to abandon eastern and central European as they did in the 1930s.
His calculus is that western nations don't value eastern and central Europe as much as Russia does.
He will move on Ukraine because it is not a NATO member.
He will move on Estonia, Latvia, Lithuania, Poland, Romania, and Bulgaria despite being members of NATO. His calculus is that western Atlantic and western European countries will not shed their sons' blood to save remnants of the old Soviet empire.
The west has historically failed to shed their sons' blood to maintain the independence of Czechoslovakia, Poland, Lithuania, Latvia, Estonia, and Austria in the 1930s.
The west will protest, but Putin will expand his new Soviet empire and demonstrate to eastern and central European nations that they are less-than-equal members of NATO and the E.U.