It seems as if people are getting pretty wrapped around the axle about what might constitute a "threat to the very existence of the state" in USSR Vlad's little brain. Is it now a hostile act committed by Ukraine using western hardware in annexed territory? Is it a russian defeat in Crimea? Is it social unrest in Moscow that threatens the leadership, due to losses in Ukraine? While I don't personally think that his calculus has changed enough to include such niche factors, I can see how there is some ambiguity with that whole phrase, given the current situation. But that is also dependent on believing some really optimistic western projections.....such as the idea that there might be a domestic uprising, or that this will result in something more than a stalemate.
That's the $64,000 question I think no one knows except the man himself. I think that is why western allies have been circumspect about what we have supplied to the Ukrainians so far, providing them with plenty of 'defensive' weapons but not many 'offensive' weapons that could strike the (actual) Russian homeland. I think he is trying to intimidate folks buy moving the supposed Russian 'red lines' but no one seems to be buying it yet.