But the trouble is WotC/Hasbro can't not publish a new edition.
The number of old core books that they can sell has an upper limit. Afterall you can still get copies of most editions on ebay or your FLGS. Some stores still have overstock of 3.x in fact.
It's a nice idea. But I can't see it working.
I would like to see some POD myself, there are lots of things I'd like to buy, but the demand just isn't there to make it work really.