The Pila website isn’t the most up to date alas, but for the last couple of years they’re closed on the 1st weekend of September, sometimes re-opening the 2nd weekend for a DH competition, hence it’s likely they won’t be open….but far from certain. The website seems to put up the summer opening & closing dates a few days before the summer opening, which has been the 3rd weekend in June last 2 years, but again, could be different this year.
You can shuttle the lower 1/2 of Pila quite easily if you’ve got enough people and suitable transport, and the Aosta valley freeride guys will be more than happy to guide and shuttle you at that time of year too.
Chamonix will still have almost all it’s lifts running then, Verbier quite a few. St Luc, Zermatt, Dorenaz and all the wee transport lifts in Switzerland should all be running too.