i see 3 apocalyptic scenarios, i better be wrong.
1. no cure, so just let the virus do its thing. Thanos finger snap. remember some are completely asymptomatic. we have a new human race of virus-humans.
2. no cure, a few islands lock up where nobody goes in and nobody goes out. (Singapore, Taiwan, ?NZ) forever.
3. a bit like 1, but virus mutates and everybody over 16 dies, civilization reverts back to stone age. 10,000 years later people go - i wonder why there is a tall green woman in new york island. i wonder how they built that. was there a civilization that we didn't know about?
This is pessimistic in the extreme. There are plenty of scenarios, far more likely than yours, where life goes back more or less to normal. A vaccine is not unlikely. Even if a vaccine fails, an anti-viral is likely. Even if an anti-viral fails, new treatments for respiratory distress are likely. Even if that fails, new strategies for living while preventing the spread of a virus is likely.