I doubt Ukraine will demand anything less than Russia pulling out of previous held lands. Russia will doubtless demand all lands it currently occupies (and maybe even ones it claims but does not occupy). Russia's demand could be cast as peace, though really it involves giving a massive portion of Ukraine to Russia. And if you're thinking that might be temporary... well, just ask Finland, which lost 9% of its territory to a peace agreement in the Winter War after the Soviet Union invaded them.