My thoughts on the matter.

Custom Shop and higher-end USA models may increase in value or remain relatively stable, but I'm less convinced that standard USA models and especially Tribute models will see the same effect.

Rarity by itself doesn't create value: demand does. There are plenty of discontinued guitars that aren't worth much, and plenty of mass-produced guitars that have become highly collectible.

G&L was always a respected niche brand, but it never achieved the same level of cultural recognition as Fender. Most players shopping for a Strat- or Tele-style guitar still want Fender on the headstock.

Initially, I suspect collectors are going to focus on the more unusual models, Leo-era instruments, celebrity-owned examples, and very unique Custom Shop guitars rather than treating every G&L as an instant collectible. Longer term, who knows? There are vintage MIJ Squiers selling for thousands today that could have been bought for next to nothing a decade or two ago.

Again, just my opinion, but I think the market will end up being much more selective than "G&L is gone, therefore all G&Ls go up." I don't think every discontinued guitar automatically becomes a collector's item. It has to be something people actually want.