The simple fact that the vast majority of boats these days are glass ...and glass, doesn't go away, at least not at the rate other materials might. There is a huge glut of glass boats sitting around unused in marinas or storage. In the old days wood or metal boats would gradually deteriorate to the point that only the most determined owners would keep them afloat, or happily for the builders, replace them. Not so with glass. There is a huge number of 70's and 80's boats out there that are still serviceable (and in some cases better built than the new crop). It can be cheaper to renovate an older model if it suits you, than buy new.

There is no doubt the market is dumping and I don't think it's going to take 20 years to bottom - more like ten in my opinion.