This is far from the "end" for the Kursk incursion. I expect Ukraine to hold the territory for quite some time as the war within their own borders has shown that fortified trenches and defensive lines eventually lead to static frontlines. These gains were possible because their force is highly mobile in barely defended areas. Russia can't put up any defenses close to the invading force because they would be in artillery range and have to put up their lines way beyond what Ukraine currently controls.

We'll see if the Russians eventually resort to human wave tactics in Kursk, which seems to be the way they approach fortified lines. But even then it will take them a long time to make any progress and they currently don't have the manpower needed for such assaults.