Seems much of it will happen in the off season. There weren't many people around the pools when we were there in December. Perhaps the only issue will be the April to June timeframe in 2022.
The Dolphin Pool is not heated, but the large adjacent South Pool is (near the bar), so that will pick up the slack if any is there.
During the so-called "off season" (which is really a misnomer for GO because it's very busy EVERY month of the year...even Jan and Feb)
there is never much activity in the Dolphin Pool anyway, except people sitting around the periphery reading and sunning, but never swimming.
If they're swimming anywhere, it's 40 feet away at the heated South Pool, or they're using the many hot tubs scattered around the property, or the indoor pool.
Over the last 5-10 years I've seen proof that Hilton Head in general, and GO in particular, have no "off season".
The island is busier and busier every year, and we have met so many dozens of people who come down from NJ, PA, NY, OH, CT, MA, etc
to stay 2-3 months at GO. We make it a point to go 2 weeks in Jan and 2 weeks in Feb, and we have become great friends with
that snow-bird crowd. We all do so much together...many planned and/or impromptu activities, dining out, get-togethers, tennis clinics, etc, etc.
We LOVE being there at HH during those times (using "extra" weeks), as much if not more than our six "real" ownership weeks in Spring and Summer.