Given the long history of STN-Istanbul flights, It would be great to have Turkish Airlines back at Stansted, who I think last served the airport in 2009/10, whereupon they moved to LGW. There has also been an increase with LCCs serving the main airport of Istanbul, such as Wizz Air's upcoming services from both LTN and LGW, leaving STN as the only major London airport without a service to IST (not counting the existing services to SAW). Hopefully MAG can convince TK to re-open STN, as this would be a major win for the airport in terms of the vast amount of short and long haul connections available via IST.
The other airline I'm thinking of is Aegean, who are no stranger to STN, having originally initiated their London operations from here prior to their move to LHR. With Sky Express joining the likes of Wizz and EasyJet against Aegean's (seasonal) service to ATH, could they be tempted to move to Stansted where there is far less competition on the same route? Granted, FR stepped in not long after Aegean left STN, however, they only serve the route once daily, and I'd imagine that there would be many more connections available if one were to fly with Aegean versus FR.