No one knows what the construction schedule looks like. All we know is that the monorail at Poly is shutting down in October, and the resort itself (non-DVC) will not open until "summer 2021."
I believe it is safe to assume the pools will remain open, and Captain Cook's, and the pool bars. Unless demand on campus picks up a lot and Disney is comfortable with closer spacing of guests and crowds, 'Ohana and Trader Sam's will stay closed until the resort opens as a whole.
Given that the ongoing resort closure is linked to both a refurb and low demand, I think May is early for a "Summer 2021" open, because refurbs are never on schedule anyway, and demand may be a challenge for a while. A lot depends on what happens over the winter from a viral and international vaccine production politics standpoint.