Distributing OGC is one way that the license gives for accepting. WOTC has distributed OGC, right?
For giggles, even though it doesn't work that way, I'm going to assume that distributing OGC means that WotC is using the OGL. The following is from the OGL.
10. Copy of this License: You MUST include a copy of this License with every copy of the Open Game Content You Distribute.
Must. It's not an option.
13. Termination: This License will terminate automatically if You fail to comply with all terms herein and fail to cure such breach within 30 days of becoming aware of the breach. All sublicenses shall survive the termination of this License.
So since they failed to cure the breach within 30 days of putting out the very first 5e book, the license terminated and they can't use the OGL anymore.
I guess they'll have to sue themselves to get their own money.