Xi Jinping is set to meet Putin in person this week. Russia has asked China for military and economic aid, and I believe they just made a huge energy deal - where China agreed to buy Russian oil and gas in rubles and in gold.
Who knows what's on the table here, but China could potentially bring a lot of support directly into the conflict. Same for Russia's local alllies.
I don't think failure is an option for Putin, and that scares me. What will Putin resort to in order to keep power to to not fail?
In my opinion, a best case scenario is one in which Putin is toppled from within and they pull out of Ukraine. Not sure what kind of odds there are for that happening.