If Russia goes for a full partition of Ukraine taking the south and east where russian speakers dominate, that gives both Romania and Moldova a Russian border, again. The partition of Moldova will be front and center, the obvious next step. But Moldova has another option, union with Romania. This is a unique situation but it is not a new one. After the 1877 partition of Moldova, which incorporated what is today the Republic of Moldova into the Russian empire, the communist revolution led to an application for union which Romania quickly agreed to. That union was undone by the Hitler Stalin pact two decades later.
Romanian politics being what they are, they have already committed to accepting such an application were it to be made again. But Moldova looked to chart its own course. With a hungry Russian bear as a new neighbor, that might just change the calculation.
Update: got my compass points mixed up, thanks +Michael Hendrickson