i doubt putin will bow to an ultimatum.
but if he's smart he's going to adapt his policy. this isn't working out how the russians originally imagined. they'd clearly planned how they would engage with a western-facing ukrainian government. and their first steps were a success from their viewpoint.
but you go a few steps down the road and providence reasserts itself and things soon get out of control. giving powerful weapons to thugs was necessary for the original strategy to work. but the use of them has also ruined it.
so now he is operating in real time.
his larger strategy of trying to control and weaken europe via russian gas pipelines is still operative. but he may have to change the form of his grip over ukraine.