I'm a tad skeptical of POD's long-term viability. I'm not sure that the hardware prices are ever coming down to a point where they can replace micro-batch printing with on-site delivery or that the output quality will ever reach the levels needed for the collectible object d'art market.
I might be less skeptical if the likes of Xerox or Ricoh were actually involved in designing and building the things...
(shrug)
Mostly I see (volume) pbook demand dying with genX and the annual catalog of hardcover releases dropping into the low hundreds with sales volume in the hundreds per copy. Pricing zooming into the high triple digits. And that is *with* POD. Timeframe: 2060+.
I expect to see that happen.