There is still construction at the Poly, notably the 'quiet' pool at the moment. I understand that other minor work is possible, but, if so, I am not sure what it might be or where or when. I am staying for a short visit in Jan and I don't expect much construction (other than that pool).
If I were going in May, I would feel that there is a good chance that construction would be winding down or perhaps even completed.
Check out Tikiman's Facebook pages to see the latest available information.Steve may have had to cut back on what he can say, but he still provides the best information on the Poly possible.
Good luck!