On the question of what comes next, most experts are predicting a long stalemate and war of attrition. And contrary to conventional wisdom it is the Ukrainians and not the Russians who would be able to better sustain this, at least militarily, so not including the horrendous costs to Ukrainian civilians. The Russians won't have their land bridge, and won't even have the two separatist provinces, because in those areas the Russian-speaking civilian population is not/no longer sympathetic to the Russians. Even those people that Putin believes are "his" people are now fighting against him. So Russian forces in these areas, along with their separatist militia allies, will be bled continuously by an active insurgency as well as hit-and-run tactics by regular Ukrainian military. And as those casualties mount, more and more Russian soldiers will surrender or defect, or simply stop fighting.
Beyond the battlefield, though, the real action will be back in Moscow in the next few weeks. Yes, the Russian people have very little capacity for staging a revolution. But one never knows. As Putin more and more scapegoats the military and intelligence establishments for what are his personal failures, those establishments will look for ways to hit back, not because they care about democracy or decency in Ukraine but rather because they care about their own skins. After all, the last time revolution happened in Moscow, it was directly triggered by massive battlefield losses in a stupid war started by an ego-maniac leader who ignored his own advisors.