One of the very good things about d20 was the OGL. At the beginning, post 2000, there was a boom of ideas and variants (both within WotC and beyond), tons of cool, different spins on the d20 mechanics, with stuff like Black Company and Arcana Unearthed and on and on with Etherscope, Spycraft, d20 Modern, CoC d20 and whatnot. Right now, we're still very much living into the aftermath of Wizards leaving the OGL in the dust. The OGL, besides the OSR cottage industry and the like, is very much gravitating around Pathfinder now.
I have this idea that things are going to go full circle at some point. That gamers are going to get tired of the one size fits all, that they're going to get bored with the optimization and everything is about the rules, and the extreme passion or hatred for everything d20, back to the beginnings, where it was more about publishing your own d20 spin for the hell of it, experimenting with this or that aspect of the system implemented on a different setting or genre, and seeing if anybody out there liked it enough to buy it.
Am I off base here? Do you think that we're going to see a sort of d20/OGL renaissance, a few years, or even decades, from now?
I've given this some thought. I think one of the missing premises in your post is that what's wrong with d20 is not *just* the emergent "optimization" issue which is a byproduct of the design - it's the simple fact that the design itself is flawed.
The emergent flaws of d20 (3.x/PF - 4e fails design-wise imo from a different philosophy but almost fully accepts these conceits) - is that optimization exists *because* the options presented are too narrow in focus and execution.
Free of context, which is how a lot of new gamers approached 3.x/PF optimization is a no-brainer. Take any attempt at creating a "traditional" melee schtick in 3.x/PF - and you'll soon realize that (again) free of context your Spartan Warrior is a piece of shit by the mechanics presented.
The optimal, two-handed, full-plate-wearing Fighter trumps all forms of non-magical martial combat, when the name of the game should be options that allow you to fully realize any concept mechanically as being meaningful.
4e is even worse at this.
This is why I hold the premise of d20 wasn't bad. It was the execution of it.
Case in point: if I wanted to make a Spartan-like warrior in 1e or 2e, the Fighter with a sword and board in 1e would work fine as is. No frills certainly. But the conceits of 1e preclude any real glaring imbalances that everyone can readily deal with.
in 2e - we get some window-dressing with things like Style and Weapon specialzation. Kits if you're so inclined. And dare we go into Skills and Options for really cinematic (for some) flair.
Taken for face value, again with the same conceits of the system against other classes, and this concept does just fine (as do any other non-caster schticks).
But in 3.x/PF - it's a hot fucking mess.
This is precisely why I use Fantasy Craft as my redemption for d20. It's much more refined, and literally gives you the player and the GM everything you could ever want in d20. The options are literally impossible to fuck up. All the classes kick ass. All the feats kick ass. All the possibilities are simply right there. And you can make it as over the top as you want, or as simple as you want.
Oh it's different than 3.x/PF - but only in the right way. I often wonder why it doesn't get as much praise as it deserves as a system simply for this reason: there are few things one could level at 3.x/PF that FC doesn't solve mechanically (because it balances everything against everything else without sacrificing optimization - because everything is *already* optimized). No Feat taxes. No LF/QM, No crappy skills, No shitty feats, No weak classes, Ridiculous amounts of options on character, GM, campaign, NPC level. It's really what 3e should have been, imo.
Whether you like it or not - it's worlds better than any iteration of 3e or Pathfinder mechanically. (if d20 isn't your thing - then ignore this post).
Will there ever be a renaissance like d20? Dunno frankly. I don't think after 3e/4e D&D will ever be the same for anyone with history with it. I think it's gone so far afield that it's just a name, with different meanings to different people. That ship has sailed.
If there will be another "gaming zeitgeist" - I'd bet it will be long in coming. I have no faith it will be D&D Next - though I'm sure a lot of people will play it.
Edit: if there was a game I'd love to see a renaissance for based purely on the community and the quality of the game: it would be Talislanta. Looking forward to the new Savage Lands game!!! woo! (but yeah - I doubt this will usher in any renaissance)