Sure, but as you say, this is an imaginary scenario, not the reality.
In reality, it's symptomless/benign for most people for 5-7 days, then in some people it becomes symptomatic, and in relatively few cases - of impaired/frail people (or occasionally people who seemed "healthy" but had some hidden vulnerability) - it becomes severe and potentially lethal. But that last part is due to the fact that it is novel and takes time/effort to fight off, not because it has some magical quality that makes it sit dormant in your system for 5+ days before it wakes up and says "surprise, you're suddenly nearly dead".
HIV is a totally different kind of virus, so comparisons to it are mostly unhelpful. Whereas plenty of coronaviruses and other respiratory viruses have become endemic and mostly-benign before.
There's no reason to believe the rate of severe cases won't decline (more quickly than 10-30 years) once more people's immune systems become attuned to it.