I think it is foolish to try to predict what Russia/Putin is up to once Ukraine has been dealt with (which, I assume, it/he will have achieved at some point in time). There are numerous reports of fact as well as opinion pieces published over the decades since the fall of the SU by esteemed and respected strategists which or who pointed at/predicted Russian military intervention, if NATO did not call off its eastward expansion plans. We have arrived at that point in 2008 already, and then again in 2014, and now finally also in 2022.
For those wanting to involve NATO and set off WW3 along with the nuclear apocalypse, I wonder - why the rush? We can still nuke this planet's civilization to scraps after Russia's/Putin's plans for re-establishing the "Great Russian Empire" have materialzied - or rather, if they actually do.
Please excuse my cynical undertone, but this reckless calling for intervention that may very well lead to a kind of catastrophic escalation that human history would never ever recover from REALLY scares the shit out of me :(