Russia would still stop because controlling the rest of Ukraine would be more trouble than it is worth for them. And they might gain some concessions from the West. Attacking NATO is a common talk point in the West about what happens after Russia takes over Ukraine and Zelenskyy is more than happy to suggest that is to be expected as he says they are fighting for all of Europe.
On the contrary they seem to be doing much better than anyone expected, maybe even themselves, and they appear to have successfully stopped Ukraine from ever joining NATO which was absolutely their main objective, just see what they have been saying since 1992.
