About the only thing I can see working is a group of small publishers, or would-be publishers, banding together to develop their own "SRD 2", sort of like a free online PHB 2. They make all their material themselves, release it freely, and agree that within their group, these will be the standards they adhere to. The actual profit would come from supplemental stuff such as adventures, campaign settings, etc, which use the material.
Essentially, this would be replicating what WotC did with the SRD, but on a much smaller scale. As to who would be in that group, I've no idea. An alliance like IPR would probably be best suited to do so, but I don't think they're doing much D20 these days.