My answer to the OP, FOK, is NO it is not sustainable. Reason - the inherant greed of those such as RYR & EZY that I think drives down standards across the board that will very soon see safety take 2nd place to bottom line.
To a certain extent this is already happening, I suspect. When decisions as to whether to anti-ice aprons or not with severe wx predicted and incoming a/c expected rest on the strain it will put on budget, as I think happened at LPL on 22/12/09 (EZY7008) leaving a full A319 sat for almost 2 hours as handlers rightly would not risk their limbs in those conditions, then we are almost there.
Also on FD, when pilots are treated worse than bus drivers and paid so (see BRK contracts at RYR and latest from EZY's recruitment practices) then pilot's self-steem dives and so does FD performance.
Add to that the airports that RYR etc have been screwing seeing the light and telling them to beggar off, the increasing likelihood of fuel taxes, improvements in surface transport and the general hassle these days of air travel like the bozos at security then I think loco will be dead within 10 years. A pity as it has served me well but I'll adapt.