They are putting in another slide and doing an overall refurb of the Old Man Island pool in January. Having been in January, it may not be warm enough to swim, anyway, so that is why that month was chosen... (it was supposed to have closed in late September).
Since you are staying at PO-R, note that there are also 4 quiet pools, and you can take the boat from PO-R to PO-FQ and use that pool. The kids love the Serpent slide there, anyway!