EZY won't close STN, it makes no sense. Contrary to popular belief STN performs well as a base with load factors and RPS high. Obviously growth has been stagnant for some time with a greater focus in LTN and LGW. STN however fits into the larger London image with 7 prime AM summer slots which are now near impossible to get. Nor would they allow a competitor come in and take the slots to compete at a London level - STN is also core to EZY's domestic strategy.
Where I think this rumour has come from is EZY thinking 'worse case scenario' with the end of the transition deal, if it goes horribly wrong then we may see the airline suspend winter ops until the pound stabilises again, however I do believe this is unlikely.