It doesn't at all imply that it won't come back.
For example, if Tiger Woods starts the front nine of a tournament at -5, someone might say he is "crushing it". They aren't saying he is going to win the tourney, just that he is exceeding expectations.
In the case of CoVID, the concern was that the number of hospitalizations would exceed available capacity. By any objective measure, we're crushing it. It doesn't mean this mutating bitch of a virus is done, it means our response has exceeded it's objective... in the present tense.
Now, I don't care for the term crushing in this case, flatten was perfectly fine. But at least I understand what it means.