Think about it, they should know the answer by now. Even if its not OGL, if they are making a backwards compatible edition, and if I make a module for it, I should be able to claim compatibility with 5e via OGL right? Are they going to make all of it OGL? Parts of it? How about some of the 4e terms they purposefully created for the sole purpose of fucking up the OGL as relates to 4e? If so are they thereby opening up 4e to the OGL retroactively if you use its weird-ass terminology?
The answer to these questions really are an important indicator of where they are coming from with respect to their customers.
That, and if they start selling the older edition PDF's again.