I believe all the WDW pools are heated, although I think they are less warm now than in the past to save $$ on energy costs. I've been to BCV in early December and used SAB...I guess it depends on the air temperature and how brave you are. There are two hot tubs. I found the pool near the beach with the kiddie slides is the warmest. The lifeguard told me since it is separate from the larger pool complex it has its own heater and it therefore stays warmer. Good Luck!
We have used SAB in Jan/Feb if the temps outside were reasonable. Coming from the midwest if it's above 60 degrees in winter we think it's a heat wave.
We were the only family using SAB one November afternoon. It's heated but sometimes the outside temps just don't make people comfortable. We swam at BLT during Marathon weekend in January and only once, the rest of the time it was just too cold.
SAB is heated. In January, the weather can be warm and comfortable for swimming or quite cold. If it's cold, it is a very long cold walk from the pool to the top of the water slide. But, the pools are heated and warm enough if you stay in them.
I enjoy the pools, especially SAB. I save my BCV points to book a vacation when I'm pretty sure it will be enjoyable swimming weather. Now for me, that would be from late April through mid-October. That's just what I do. I wanted my family, the DGC, to experience SAB for the first time, and that was in November, and it just didn't work out that year. It was way too cold. I have the family booked there next June!
We have gone in March for several years in a row, and we've always had sunshine and fabulous weather. The temperature has always in the high 70s to mid 80s, and we always swim.
We're going in Dec this year (12/22 - 12/30), and I think the weather is much more "iffy." We went the week before Christmas a few years ago, and it was sunny and 80 every day.