Of course it will.
>ground troops from neighbors, EU, and possibly NATO
They are not suicidal, I don't think.
>Russia “saving” a brotherly nation goes flying out the window
Yes. That is the reason war will continue the way it is now: very slowly, and stupid.
Edit: reddit spacing
I'm afraid something as drastic as the annihilation of Kiev will lead to actions that are beyond the usual risk assessment levels. Countries will be compelled to act, (repeated...) threats of nukes be damned. Europe will not tolerate another Nazi Germany on its borders, period.
Put another way, a massive, discontinuous step in escalation will inevitably lead to a similar step from the other side. There is no world in which Germany and Poland go "OK then" and withdraw all aid.