If Putin is not stopped in Ukraine, he will undoubtedly go further... This will only stimulate his appetite, and Putin will advance further into Poland and the Baltic states.
I believe that Putin has already lost this war. It’s clear that he won’t be able to win it. The goals that were initially declared—capturing Kyiv, denationalizing Ukraine (which, in simple terms, meant stripping it of its sovereignty), and demilitarizing Ukraine (which meant taking away its army and ability to resist)—essentially turning Ukraine into a puppet state under Kremlin control—are obviously unattainable.