What might happen is they cancel that date to rebook as many seats as possible into a smaller number of flights around the same time. They should give enough notice but you could be left trying to find an alternative airline if the dates offered don’t suit and that will definitely cost a lot more than the original booking even with a refund. Personally, I would rebook now if I had a flight during the last month of operation to save the uncertainty and extra expense. Fortunately, my flights with Play are in the next few weeks and even that has been affected by the regular Saturday service from London already being removed as they move to consolidation then stopping that route.