Well it goes both ways, we can neither assume long term immunity nor lack of long term immunity. But it's not even a binary: the most likely outcome (by far I

Well it goes both ways, we can neither assume long term immunity nor lack of long term immunity. But it's not even a binary: the most likely outcome (by far I think) is that strong immunity of the quality that keeps you even from becoming a symptom-less spreader for a few days won't be lasting, but infection will never again be as dangerous as it was the first time (or would have been the first time, without a vaccine). The immune system is a memory hierarchy.