The answer to that question is really quite complicated. There's still a significant amount of people that have never been infected with it, and vaccinated people are still catching and spreading it. The majority of spread in the vaccinated and unvaccinated populations are in the virus-naive, so in theory each successive wave should have less fertile ground, but given how much easier delta has spread, it doesn't need as large of a fertile population.
I think we have a couple intriguing test cases that we will have to see how they play out over the next 6 months. Those two tests cases are India and the gulf coast/Florida. The Delta variant burned through both of those places largely unimpeded, and both have dropped to their lowest levels of infection since the start of this whole ordeal. India is 5 full months out from the peak of their massive wave, and there's no signs of even a bump so far in India. Are they done with it? Or is it a lull before another wave? Florida currently has the lowest case rate in the US and it is still dropping, are they basically over it after this last wave? Or will they still see a significant winter bump?
As time goes on, cases become less relevant and hospitalizations/deaths should be how future waves are measured, unfortunately those haven't decoupled as much as we would all like yet.