Are car manufacturers/dealers likely to heavily discount such models to shift them?
This is the general tactic, I think. You get more toys and they cost less – because the cost of R&D for the car (or at least the changes since the last model of it) have been absorbed.
If you want to sell it in a few years it’ll be competing with all the new model ones that are only slightly younger so the value will be lower. But it depends on the car I reckon.
Passats didn’t change much visually or mechanically (and barely at all internally) the last facelift, so my 2006 one still looks fairly current. However go back a year to the model before that and they look really old fashioned.
However some new models are a significant jump. The newer model Prius is not only better looking than mine, but it’s quite a bit more powerful, more economical and more refined, a much better car.