Yeah, they explicitly had that FAQ on the OGL with stated that it was in WotC's best interest never to make a worse OGL since if they did that people would always be free to use a prior version, as explicitly stated in the license - that sure sounds like a promise. It also sounds like a description of their interpretation of the contract, which is also relevent.

The OGL does explicitly use the phrase "in consideration for", which you'd hope would make this non-gratuitous. Then again, IANAL.