I made a somewhat educated guess. I'm not as educated as the people you name, but they too are just guessing. I'm trying to be reasonable though, and I don't have any reason to spread an optimistic hope.

If this is the only vaccine that passes trails - well they can't make it fast enough for a late 2021 opener. If some of the others also pass trails then early 2021 is a possibility (so long as you don't have some reason to prefer a specific vaccine as opposed to whatever you can get first)