@Clark
What I meant with the "GSL won't open up the rules as the OGL did" is that the GSL (probably) won't allow the reprint of the rules verbatim (such as the OGL allowed with the SRD). I find that a bad move from a consumers point of view (I'll elaborate in a second), but a brilliant move from a business perspective. Why do I think It's bad from a consumers perspective? If WotC decides on another edition, the then supplanted edition can't officially be supported anymore by third party publishers as it is now. In short, it doesn't allow for a fork in development, thus if you don't like the direction WotC is taking the game your out of luck. I'm certain that no significant portion of the D&D player base will stick with 3.x for long (too many gamers want the new bling-bling). From WotC's perspective the 'forking' of D&D is a bad thing, they don't want their flock diminished by different versions of their game.
Obviously WotC sees the advantage of integrating third party publications into their IP. That's why there they hint at opening up more of D&D, if that means mindflayers and beholders are opened up needs to be seen. While I hope that the GSL will be better supported then the OGL, similar promises were made by WotC employees when the OGL was released, after the initial rush of Psionics/Epic/Gods it became awfully quiet. The same might happen with the GSL, despite all the best intentions of the current WotC employees, I just hope there won't be a round of firing like there was after the 3E release.
@JohnRTroy
I highly doubt that WotC felt any negative effects that weren't canceled out by the positive effects from the 'free' releases of the SRD. Sure there are many folks that said and continue to say that they'll never need a PHB because they have the SRD. I'm certain that 99% of those folks would have been as happy to use a 'pirated' copy of the PHB/DMG/MM if the SRD weren't available for 'free'. The 'free' versions of the SRD were used as 'light' rulebooks, because WotC couldn't keep up with the technology curve. Their digital initiatives failed miserably (character generator) or were horrendously late (digital versions of the rulebooks). While their efforts this time around do seem better, so seemed their efforts for 3E (anyone who remembers what their toolbox would do, will see the features repeated with their new efforts). I don't know if WotC lost many sales to games such as Conan, Spycraft, M&M, etc. Because my 'common' sense tells me that a lot of the folks playing those games might very well have moved to other game systems if the OGL variant systems weren't created.
The ability to revoke the GSL for any other reasons the not following it, I see as bad! Very, very bad! Not only publishers invest an enormous amount of effort and money into third part product lines, so does the consumer. If for whatever reason WotC decides to end the license, it means no further third products can be made, a logical time for that to happen would be when 5E is introduced (possibly under yet another license, or worse, no license). With all the changes a company like WotC (and their parent company Hasbro) go through, I have serious doubts about how much one should invest in a game and licence that could be yanked at any time. I'm pretty sure I'm not the only one.
@General
I'm wondering if it would be prudent/profitable for third party publishers to release products under a dual license? But because in this case the licenses are connected to specific incarnations of a game system, it would need to be more then just dual licenses, the content related to the license would have to be different. Green Ronin separated their 'fluff' and their 'crunch' with their "Pirate's Guide to Freeport", they released a shorter rules booklet for True20 and D20, they could even release a 4E version. You would sell your customer effectively two books (the 'fluff' book and the 'crunch' book), the core product ('fluff' book) your trying to sell would reach a wider audience (more sales), the secondary product ('crunch' book) would share resources across multiple systems (art, layout, concepts, some writing). Most 4E third part designers would come from a 3.xE background, so should be intimately familiar with both systems, so they could develop for both systems. It would of course take more time to develop, and people would need to be paid for that work, the question is "Would the extra sales compensate the investment?". Not every product would benefit from this approach, but I think many would (a new ToH for example would work for both systems).
