in April, D&D Brand Manager Scott Rouse said this in an interview on ICv2:
Scott Rouse wrote:
"...in June of 2008 [the d20] license will be terminated as we release the new game system license. We're going to give publishers a sell-off period where they'll have until the end of 2008 to move through any stock that they have in their warehouses. Once it's at distribution or in retail, the product can continue to sell through in its natural progression. We're not going to ask publishers to recall that product and destroy it. But any excess inventory that they may happen to have in their warehouses at the end of '08 would need to be destroyed. Any subsequent reprints they can still publish through the Open Gaming License, they just have to remove the d20 system trademark logo. That would include both PDF and physical product that continues to be sold after 2008."
...but, as far as I've been able to tell, there's never been an official announcement that this plan was actually carried out, in June 2008 or any other month. I'd expect notice to be posted on Wizards' d20/OGL license page, but I don't see anything like that there.
Nevertheless, numerous third parties have taken that statement as fact, and have begun the process of rebranding their d20 PDFs as OGL (or planned to stop selling their d20 PDFs entirely).