The torrent of better quality OO models at relatively modest prices, that the UK enjoyed from 2000 to about 2012, is going to begin 'resurfacing' in earnest sometime fairly soon. That's my assessment based on the average age of customers frequenting model shops during this period. (I well recall one very amiable gent who had ordered such quantities of Bachmann's products that had literally arrived 'all in one go' that two of us customers in the shop helped him and a staff member move the heap of loot to his car, since he could in no way carry it unassisted.) I anticipate that this will have an 'interesting' effect on what new OO RTR product can be sold for, let alone s/h prices.
I'am not too sure, I agree with you in theory they should be a glut of models made in this period as the buyers or their relatives start selling stuff off.
My doubts are based on experience of these models I've quite a few myself, some hardy used still in box, problem is they are firstly not durable I've had problems with mazak rot, wheels de-quartering, fragile bits falling, gears not meshing.
Secondly they are not easy to repair, parts are differcult or impossible to buy, use them on the layout the odd one suffers a derailment things easy break, not so easy to fix
Once enthusiasts get to know a certain manufacturer or model has a common problem, the models can become worthless, good example of this years ago was a well known make of "N" locos with a spilt worm gear, rarely seen 2nd hand because none work and differcult to fix. It would be interesting to see what hattons Garrett only 200 made will be worth in years to come
Reason why even tatty bashed about examples of Hornby "O" &, Hornby Dublo still fetch reasonable prices, they still work, easy to repair, easy to strip paint and repaint, you might not get much but you will get something