In my opinion, the operation around Kiev is meant to pin a large portion of Ukrainian forces in the northwest while the Russians solidify their land corridor to Crimea in the southeast. It seems like the latter objective is now nearly accomplished. I would assume that an armistice at this point would trade that corridor for a withdrawal of Russian forces from the vicinity of Kiev and other areas of the north.
Bingo. Kiev has NO VALUE to the Russians, but means everything to Ukraine.
The Russian pincher move is almost complete in the south.
They will get most of what they wanted.