Agreed things are looking bleak at the moment but we need to wait and see how thighs pan out. So far RyanAir has only threatened to move operations and its new hangar abroad and easyjet has also only threatened to move as far as I am aware. This may be subject to change depending on how the government decides to reinvigorate the economy and persuade businesses to remain in the UK. Future concessions or tax breaks may encourage some airlines to remain under a UK AOC.
I am concerned how the aviation training sector will endure though. It may become difficult for EU aviation students looking to train at the leading flight schools such as CTC, Oxford, Aeros etc to obtain a student visa.