As far as OGL, I think the cat is out of the bag. Copyright covers the text and images they've created for 4e but *not* the game mechanics. If WotC suddenly vanished, the good parts of 4e would be cycled into a third party d20 SRD derivative that combines the best of both editions.
...In fact, that may have already happened (*whistles innocently*).
What would amusing is somebody actually creating a retro-clone of Heinsoo 4E D&D (ie. 2008 -> 2010).
Though I suspect the 4E Essentials "Rules Compendium" + "Heroes of the Fallen Lands" books, would be easier to "retro clone" than Heinsoo 4E.