Realistically, based on geography, I wouldn't be surprised if Putin marched into Moldova the moment Ukraine is even half-subdued - enough to give him any forces to spare. After conquering Ukraine, Putin will after all automatically have his army covering Moldova's entire eastern border.
One of the few things that I hope may give some long-term cause for hope is if sanctions continue to be ratcheted up, I imagine it'll become extremely hard for Russia to keep manufacturing advanced weaponry, so they may get to a point where, once they used the stuff they have, that's it (unless China starts selling them stuff). Ukraine on the other hand will be able to just keep continually topping up, provided NATO continues to supply them. If that theory works out, eventually we'll hit a point where Ukraine has weapons and Russia doesn't - and at that point, Russian forces in Ukraine are toast. We just have to hope that enough of Ukraine's army can remain intact long enough for that to happen.