Western support has already been factored into this offensive in the sense that the Ukrainians have been waiting and receiving, and are now integrating, the tanks, the artillery and the ammunition.
The calculus is that this offensive has a reasonably good prospect, at least at the operational level, because of the western weaponry and the training that has gone into it. However, this will be expended. Then this question comes: After both forces have used up their energy at this level, what happens in the fall and what happens, as you said, as winter comes?
These are the calculuses. That's four or five months from now, after a major battle. It's very difficult to guess what will happen, except that the calculus is always this: “What's my advantage to continuing the military action?” versus “What's my advantage in a ceasefire?” Both sides will do that.