I doubt we'll see the games completely drop off, but I think some of the recent sales that are high are not an accurate representation of the intrinsic value of those pins - no more so than a great deal suggests that a pin should be valued much lower.
People see a game go for 2-3k what they're normally used to seeing, and they panic. It's a small enough community that we fuel these prices very quickly compared to other, much more robust, markets. If you see your game sell for a high dollar amount, at least part of you has to question whether your machine is worth that kind of money to you.
I think a lot of the rise is attributed to Pinball Arcade, or even FX2, it's reminding people about pinball.
Let us also not forget that there are other things that will have an effect on the pinball market. New technology elsewhere, for example. For those of you who do not follow video games, the current consoles are pretty old, over 6 years old. Within at least the next couple of years you will see new consoles. These DO act as an alternative for the entertainment that pinball provides (at least to a lot of people, particularly those who have been brought IN by video games like pinball arcade). They're cheaper, more versatile, loaded with technology, and who knows that next gen will be capable of.
We've seen the video game market have a real effect on pinball before. When the frustration of trying to find a reasonably priced machine becomes too much, I wonder how many will flee to substitutes. I don't think it will necessarily make prices plunge, but it could certainly have an interesting effect.
Just a thought.