mxyzplk
Explorer
It seems like your assertions are based more on the gaming business climate of 2002-2005 or so - nearly all these companies you keep listing as not jumping on the GSL bandwagon had already fallen by the wayside months before 4E was even announced.
Green Ronin, Necromancer, Mongoose, Fiery Dragon, Malhavoc, Kenzer, and Goodman were about the only "big" viable d20 publishers left at the time of the 4E announcement, and of those, only Goodman was releasing anything with a volume approaching that of the days before the d20 bubble burst.
You can certainly trot out a long list of publishers big and small that haven't produced GSL product, but its ultimately meaningless - they're not producting OGL stuff either.
Its easy to forget that the D&D-related games market in 2006-2007 was dwindling away...
It had reduced along with the overall RPG sector's sales, but I don't think "dwindling away" is fair. In fact, those companies *are* still producing OGL games. They were producing d20-branded games too, but Wizards revoking that license means they have to burn their stock on Dec 31 of this year, so I don't think that can be held against them. Since a lot of that d20 stuff was OGL it is of course putting the hurt on them and some are turning to new lines that don't depend on the OGL, but they are indeed still publishing OGL stuff to this day.
Let's take my list - "Ronin, Paizo, Necromancer, Troll Lord, Kenzer, Postmortem, Wolfgang Baur, Monte Cook, Sean K. Reynolds, Deep7, Highmoon."
Green Ronin's stuff is mostly OGL. Mutants & Masterminds and True20 are and those are in active release.
Paizo's stuff is all OGL, even Pathfinder.
Necromancer was still publishing stuff till the GSL confusion hit - Rappan Athuk Reloaded, heck City of Brass just came out in September. They're still trying to figure out if/how to go 4e, but only ramped back after the announcement.
Troll Lord - Castles and Crusades is OGL and they're still publishing it.
Kenzer was all d20 but was publishing up until the news hit - now, sadly, you go to their HackMaster Core page and see the notice "Our license agreement with Wizards of the Coast has ended. This means that certain rulebooks using material from TSR/WotC products, or the D&D logo, are now unavailable from our web store." They're working on a new HackMaster version now.
Monte and Wolfgang are doing their own OGL things.
Mongoose has whole OGL lines, like Conan, they are actively publishing.
We can discuss what "in volume" means, but all these companies were, and still are, producing OGL games and supplements. Some smaller publishers had fallen by the wayside but not these guys - at least, they were still in business doing exactly that. There was a bit of a d20 glut and bust but there were plenty of companies like these still playing mainly in the OGL space and being successful up till the announcement, and a surprising percentage of those (mainly those that didn't depend entirely on the d20 license) are doing so up to this day.
That's why they won't touch the GSL - it's more like the d20 license than the OGL really. As these companies sell all their books for $2 on paizo.com and look around at the crates of stock they'll have to burn at the end of the year - I think we can see why.