I own a resto company and many of the companies that I've been talking to won't replace many of their parts once they're gone. Sales are not that great and many of the cars out there have already been restored. If you need a part, you better get it now. I'm buying up several thousands of dollars worth of parts for a few of my future resto projects.
Most of the parts at BEA and PG Classics are a one run only. Get them while you can. Supplies are already low on several part numbers.
You will never, ever see this many resto parts again. I promise you that.
I think as the demand diminishes, the smaller companies that were able to jump on the bandwagon will drop out, and only the big names with the financial backing (Year One, Classic Industries etc) will keep on going.
The bigger parts - body panels, grills, interior trim etc - are what will consistently be produced, while the smaller obscure times may only get re-produced once every few years in smaller batches - rather than having an endless supply of stock that won't move.