We may be on the verge of at least what happened to Czechoslovakia in 1968. But I fear it could turn into a repeat of the Hungarian Revolution of 1956, where thousands were killed in battles between Hungarian and Soviet forces.
Russia is looking at the novorossiya. With a suitable pretext, it could march in and amputate the primarily Russian-speaking oblasts in eastern Ukraine and never leave. The only question left to be answered is what could constitute a future pretext for Russian intervention.
The US had no idea were those armies were until they turned up in Czechoslovakia. Now we know exactly where the Russian division is located.
Not that the US will or can do anything - since we withdrew our armies from Germany.
The Ukrainian mil is too weak to do much but run or die. The civilians are likely unarmed as well - which leaves Molotov cocktails and occasional sniper fire from hunting rifles ...
But, yeah, if they meet resistance, it will be a blood bath.
Of course, there is the possibility that the Russian will just move their troops into one of the many abandoned mil bases and call it good.