But I get what your saying. Honestly I think they would best be served by stopping all edition creation altogether and just create content for 1e, 2e, 3e, and 4e. Have a supplement, create rules for it that can be used in a multi-edition platform for which everyone will by as it's based on their preferred style. A Races of Giants book, for example, would have rules and stats to use Giants in EVERY edition they have out. Then there can be multi-platform rules that are useful regardless of edition.
I could see that not working so well, since:
for any given book, only about 1/4 of the stat material would be relevant for most gamers. I suppose for flavor material that might not be a huge issue, but would probably factor into how people make purchases.
Basically this would be just Adventures and maybe the occasional splat book here and there or Setting specific books where the rules come into play. Also, there are supplements that can be edition neutral yet provide setting (generic at this point) features that can be used across editions. This might be world building ideas or certain rules on providing for large scale wars or engagments or supplying an army, etc. These can be separate from actual edition specific rules.
You would also need 4 different authors for each book, since I would imagine that it would be really difficult for one person to write for four systems all at once, without some rules confusion and inaccuracy setting in. Or you would have a much higher level of editing required. Either way, not sure how cost effective it would be.
Currently you can purchase the Sundering adventures that are utilizing the D&D: Next ruleset. They also have PDFs that you can download for free that covert the monsters into v3.5 and 4E right now As seen here. So they're already doing it, which I think wouldn't be too hard. And if it's put into v3.5 then a conversion to Pathfinder is pretty easy-peasy.