I doubt this. OD&D, BD&D, 1e and 2e all still have players, even through none we're open. The release of 5e will create a new generation of grognards who think that 4e was the last true edition of D&D.
Very true, but the difference is that 3E will continue to be actively supported. The GSL prevents that from happening when WOTC moves on to 5th edition. The only way 4E will be supported will be via the OGL route, which Goodman Games has proven can work, at least module wise. OSRIC, and other OGL versions of 1E and OD&D have shown how 4E rules can be supported once 4E is cast aside by WOTC.
The question will be will people try to do it? IF they make one mistake in supporting 4E via the OGL WOTC will jump all over them. Yes, WOTC will do so, to keep 4E from competing with their 5E sales like 3E is competing with their 4E sales.
So 3E is the one safe bastion of an alternative D&D to whatever WOTC does. Even OSRIC and the others have to tread carefully, very carefully, and anyone who tries to support 4E after WOTC moves on will have to be even more careful.
So 3E is the most viable alternative to riding WOTC's coat tails, and the decline of sales at the announced end of 3E showed those companies that riding WOTC's coat tails is not exactly good for the long haul. Plus, if you thought the GSL for 4E was, or still is, bad, what odds do you give for 5E being friendlier versus even more controlling than 4E's?
If you want to try and ride 4E's coat tails you can do so without signing the GSL, Goodman Games and Kenzer have shown two ways. Unfortunately a lot of people don't like buying "generic" over the "name brand".
So if anyone wants to create a viable company that can hire and pay regular employees, 3E OGL is the most stable platform for such a company to do so.
So 3E/Pathfinder is around to stay, far much more so than any other edition, all because the OGL allows for continued support, and 3E is getting that support. Paizo is now the TSR/Original WOTC of 3E/Pathfinder, and due to the OGL Paizo has to share the market with whomever wishes to enter it. Paizo's edge is their history, established customer base/visibility, great customer relations, and extremely high quality products. So they are likely to stay the leader in the OGL D&D market.
Plus if your a serious gamer, and play things other than "D&D" like I do, staying in the 3E market with Green Ronins Mutants and Masterminds (with True20 being a very cool alternative to "standard" D&D), and all the stuff Mongoose is supporting, the OGL businesses are a good community to stay with.
Heck, even my favorite company, due to Castles & Crusades, Troll Lord Games, has moved into Sci Fi with StarSIEGE, and is moving into the super heroes market, horror, and others. They are OGL as well. They are growing, have their own Dragon print magazine in Crusader print magazine, which just grew to 36 pages, and are planning to grow to 48 pages in a year or two. Plus their support for C&C continues to grow with awesome stuff like the forthcoming "Of Gods and Monsters" written by the lead author of "Legends and Lore", who is also Editor in Chief of Crusader, James Ward.
Plus the CKG will finally be out by the next GenCon. They are also putting out modules almost monthly now.
So yes, the OGL is a very good gaming market/community to be in. I just wish my finances allowed me to buy it all.