It really does depend where things are going.
LTN has a usable runway with good connections to London.
Even if looses thes LOCOs there msut be marrket comprising business jet and premium business travel - so Harrods, Signature and the likes of SilverJet. may be the locos will go.
Furthermore as a Milton Keynes resident Stansted does not serve me at all, so my real options are LTN, BHX or EMA or CVT (LHR or LGW for long haul but I wouldn't touch them for short haul). I am sure arilines will want to serve this market. None of these ariports has anything compared with proposed LTN expansion.
At least one politically active acquaintance of mine just sees runway capacity putting air travel pricing back to where it was - one trip a year for the masses and serving business need, slot prices pricing the loco's out. If he's right then we won't need increased capacity.
I don't see Luton dying - if it stuck with its infrastructure it is likely to simply serve those who can afford to pay.