AP did the WYWH SACD recently and the DSOTM SACD on preorder (admittedly on preorder for a long time; although not nearly as long as the Roger Waters' 4LP 45 RPM of Amused to Death which has been on pre order for YEARS. FOR. YEARS...)
I don't see it out if the realm of possibility. Does RW need to sign off on REs? Don't the other 2 control licensing?
I'd be down to see The Who get a release. Less excited about about Zep. And I think Page would be a road block. I think he'd want to have his hand too much in it rather than just license it.
If they did Led Zeppelin (or the Who for that matter) surely they would use the metalwork from the classic issues, it shouldn't be that difficult to sell.