We went in December and while the pool was heated, the air was chilly and made swimming for DH and I uncomfortable. Our kids still swam, as kids will do, but only swam once.
The pools are heated; you have to ask yourself if you can make the walk to and from the room.
"Cold" is a very subjective term; it depends on what part of the country you are coming from and how much you tolerate the cold.
I can tolerate the cold a lot more than most people; to me 50's is still comfortable. I don't get cold until it gets down in the 40's and it has been known to do that in December.
I would look at the nighttime temperatures a few days before you leave and decide if you can tolerate that temp.