At the risk of sounding tedious, there will be no dramatic increase in legacy longhaul at STN, for two reasons:
(1) premium business is at LHR and that's where carriers make their money;
(2) there is, and always will be, insufficient connectivity at STN.
I don't think Stansted will attract a great deal of long-haul although it may well get a bit. I think more winning traffic from Gatwick and Luton and attracting other short-haul airlines and LCC's.
Was LHR subsidisng STN out of its profits, or was STN subsidising LHR for its infrastructure improvements?
Heathrow's had in the last decade a new control tower, Terminal 5 and now doing the new Terminal 2 not to mention all the other improvements they've made. Stansted has had nowhere near the level of effort that Heathrow has had.
The fact that BAA spent 3 years fighting for an airport that continued to decline clearly shows that STN was subsidising LHR. There is no other reason as to why they would want to keep it if it was genuinely a failing airport with little growth in the future. The truth is, BAA (or Heathrow Ltd. as it is now) only have eyes for Heathrow. They didn't want to lose Stansted because it would effect how much they could spend on Heathrow. It's as simple as that. They can't have subsidised Stansted because they haven't invested nearly the amound that they have at Heathrow.
Anyway, point over. Need to remember that this is the Manchester thread.