I hope we never have to find out, but as long as Putin is breathing I don't think we can discount the possibility.
Russia is losing 30k soldiers a month. A month. For many months. They have probably lost more than 1 million soldiers during the course of the war. They are sitting with sanctions from most of the western world on them, cut out of swift, isolated from the rest of the world other than China, India and Iran.
And there are no signs of cracks in the regime. There is no nation in Europe that I would put up against the Russians for capacity to suffer without breaking other than Poland. And that's just because the Poles know what happen when they lose wars.
China isn't willing to eat a nuke over what it can get for cheap.
Taiwan also isn't nuclear armed.