That's one thing about modern stock. So many trains only run in specific parts of the UK (168, 175, 185 etc) that there won't be the same "farewell" for any modern units
I wonder if some of them will move around before the end of thier life. The HST's were UK wide anyway but will the 91's do some open access routes before they retire, the 180s are becoming well travelled now!
Looking at a lot of modernish units they have got around a bit.
150/1's were really only the Midlands and Wales (I know the ventured to Ipswich and Leeds as well) but they have hit London and the North and SouthWest now.
150/2's have gone lots of places
153, 156, 158's were nationwide from new.
165's because of the loading gauge have never really moved and probably won't
I suppose it is the policy of short specialist builds that have caused the problems. A 168 and 170 are really the same thing, but the 175s may go elsewhere is the routes were ever electrified.
It is hard to say what we will have a softspot for when they go, the 156 probably for me. The 114s have a place in my heart because I grew up with them, but did prefer the sprinters when they took over (but not the pacers)