I will also give Professor Snyder a chance to answer the question, but as far as Transnistria is concerned, I would say that it's possible. On the other hand, the Transnistrians are careful not to state their position on this—unlike South Ossetia and Abkhazia, for example, which were quick to recognize Donbass, Luhansk and Donetsk as independent states and support Russia's invasion of Ukraine—because Transnistria has other interests. Even though it has close ties with Russia and relies on it for gas, finance, military security and so on, it also deals with Europe. More than 60% of Transnistria's exports go to Europe. So there is some interdependence.
For the time being, Transnistria doesn't seem ready to step in with its own army to support the offensive on Odessa. However, nothing is off the table, because Transnistria has a Russian military base under Moscow's command. So Moldovans certainly have good reason to be fearful of that.
However, at the moment, the Russian military is very much lagging behind and I don't believe it has the capacity to go that far. I believe that Mariupol is the strategic point that Moscow is going to go after. Eventually, if everything drags on, Transnistria will also be involved.
As far as a palace coup goes, I don't think we can count on that happening in the short term. It's something that might happen in the medium to long term. In the Kremlin, all the leaders close to Mr. Putin, like the oligarchs, depend on him to maintain their wealth. He has surrounded himself with people who believe, as he does, in the idea of making Russia great. So I strongly doubt there will be a popular uprising. I feel it would only be possible in the very long term.