I think it's quite difficult- once the ball gets rolling and Gorbachev indicates the Soviets aren't going to crush the opposition this time, it's sort of all going to spiral out of control for the Communists, even if not the Soviet Union itself.
On the other hand if the USSR does decide to quash dissent then I can't see how they don't just roll into Poland and try and stop the whole thing, either succeeding or failing and accelerating the 'hey we can do it too' tendency.