There is none, it is just speculation/hysteria like so much else about this virus.

There's been only a very few cases globally where a person who previously tested negative later tested positive, for which a test giving a false negative is a much more likely explanation - especially as these cases were early on when tests were more unreliable. Otherwise - everybody else who tests negative does so consistently.

The virus is very similar to the original SARS (genome about 80% the same which is huge). It is a relatively stable by virus standards not mutating massively. In fact, if you had SARS your are likely immune from covid19: https://marlin-prod.literatumonline.com/pb-assets/journals/r...

So the general scientific consensus I have seen is that there's no evidence to suggest covid19 is some sort of supervirus that will reinfect people and defeat your immune system.

There's also been some animal testing on reinfection : https://www.biorxiv.org/content/10.1101/2020.03.13.990226v1

Yes, reinfection is speculation and limits the virus to infect the population is speculation. Beyond the situation of the virus growing exponentially, there are few certainties.

I add this point because most of speculative arguments are used to claim allowing the virus infect a large portion of population won't cause much harm.