I believe MAG have expressed an interest in buying STN. Keen to get a foothold in the London market place as I recall.
It might be worth noting that the other major disadvantage STN has against LTN & SEN is that it is regulated along with LHR & LGW. I hope we can accept that STN cannot seriously compete with LHR regardless of ownership - LHR being a hub airport. LGW is arguably a different catchment area from a European route perspective so many routes can happilly co-exist at both airports. Longer haul, well maybe a new owner might have some initiatives to attract more routes but I suspect it will take a financial upturn & some considerable time / effort before that comes to fruition.