I understand your hypothesis, however I don't agree with it. I love the in-depth analysis and discussion that can be found from sites like
Travel Data Daily – Big Data and Loyalty or similar (very learned people in their field). Generally dumping a lot of seats cheaply only happens in certain limited circumstances (poor forward sales due to increased competition, or economic lethargy; perhaps a block of seats being returned by a travel agency - like will be happening now with Thomas Cook).
I disagree. It will push fares up in the short term for those actually on holidays, that don't have a return flight and who need to return to their original departure point before the uplift is organised through the UK government. Then when all the seats are returned to (or taken back by) the airlines (as TC will have been given blocks of seats to sell on many flights, with many airlines, for up to the next 355 days), this will cause a glut of availability. Some will go back into normal inventory (those they believe can be sold in the noral course of business), some will go to stressed inventory sales (ie. those seats on flights within a short time before departure - to other TA's, or flash sales by the airlines). Insurers will assist those that were wise. Not sure if there is a UK Travel fidelity fund or similar, will be interesting to see what happens for those caught unwittingly.