I think all but the really best old games will plummet.
Many new titles coming out with much more advanced ruleset and theme integration.

There is zero appeal in old and simple titles unless you have a barn full of old crap games.

A modern collector with room for 2-8 titles will have almost zero interest in having fishtales or such in their home-collection, esp if they are overpriced.

Also over time, you may feel prices going up, but honestly, compare to other real values as land or gold, and you will soon realise it s not prices going up, its money going down.

Absolutely. The whitewater, fishtales, no good gofers etc are still nice start up pins, but nobody will buy them if the cost are to high.
With old titles going for 8k, i assume you mean TZ, TOM and the likes?
I dont think it´s new collectors picking up thoose. It´s large collectors, just missing that one rare and exclusive pin.

On lower grade pins going up abit:

I´ve noticed the same over here. There was recently here in sweden a diner for 3.5k, but if you look at them and their lack of sound, depth etc, they are seriously lacking. They honestly dont belong in that price range, but i think a few will go high, but that´s for some crazy large size collector.

What´s interesting to this is also how semi to semi modern game will fare. What will happen to mediocre early spike titles price wise?

As i said before, the best titles will keep and if keept well maintain even gain in price. But i wouldn´t be surprised to se a bk-pro go for under 2k in two years.