On the question of a ceasefire after the offensive that's coming in the summer, the question is, how successful will the Ukrainians be? The Ukrainians have been very skeptical about ceasefires. They see a ceasefire as a temporary recess for the Russians so the Russians can then get their act together and continue the war.
On the other hand, there may come a point in time—it may not be this fall, and it may be next year—where both sides, Ukrainians and Russians, are militarily unable to push each other any further. If you come to the point where further military action does not advance your political objectives, then the question is, why are you continuing to fight?
An example is 1953 in Korea and the Korean War. It ended finally when neither side could push the other and it was felt that a war of attrition had reached a level of exhaustion and therefore peace or a ceasefire. In Korea there's no peace. It's still a war, but it's a ceasefire.
On the question of the ceasefire role in the Russia-Ukraine war—it's not exactly the same situation—a ceasefire would come when it serves the interests of both the Russians and the Ukrainians. They both have to want it more than the war, and there are no guarantees that it would be a continual ceasefire.