There are some indications (from 2 3PP) that DDN may use the OGL (or at least a much less restrictive license than the GSL). It seems they want support from 3PP. Dale McCoy (John Brazier Enterprises) and Dias Ex Machina (Amethyst setting) both believe so based on coversations with WotC employees and others close to the company. That would certainly bode well for support materials for DDN although you have to wonder how, or if, this would integrate with WotC's online tools...
Interesting. The speculation has been going on on ENWorld for a couple of days. I started wondering about the possibility after 2 3PP indicated they had heard the same thing. I guess we'll see.
Be more interesting to contemplate Paizo being able to mine 5E for ideas for PF. I mean if an OGL is in place why not?
Because it's easy enough for them to include a line in the license that says that the NEXT license can't be used or combined with any other license.