They probably can’t become a major force like that without full mobilization, and Putin has shown he’s unwilling to do that. For good reason–it’d probably end with him committing suicide by three bullets to the back of the head. They’re not going to be able to mount any kind of new offensive without that.
At the same time, Ukraine can’t mount any kind of counter-offensive without material support. The scenario here is either Ukraine puts up with losing territory in a negotiated peace, or things quiet down into border skirmishes for the next year with Russia sending missiles into Kyiv every few months.
Despite the headlines, there isn’t much chance of Ukraine outright losing. Russia can’t mobilize enough to do that.