Yep, I think the vast majority will. Many companies are allowing remote work for the rest of 2020 with no change in compensation. Once that ends, I'd expect people to come back. I think probably another driver of the decreased rents are the recent college graduates that had no reason to move to SF once the virus hit and everything closed. I'd expect them to move to the city once things get back to normal
On the other hand, there might be a fair number of people who move to comparable but much cheaper locations (and given the insanity of SF, that includes most other major US cities) while still trying to work remote indefinitely.
Yup, I suspect many of those live in SF want to be in a city rather than suburbs, but they're not tied to SF specifically. They just choose SF because that's where the jobs are, and would just as happy in a different urban area.