From the interviews I've done with the Paizo team, I think the issues with the magazines, the issues with the GSL, and the loss of the Star Wars licenses have turned them off doing anything but their own thing right now. They've said that even just the huge amount of art they paid for that no longer belongs to them would have been a huge part of that consideration. When we interviewed Lisa Stevens on the subject, she goes into all of that. And there is also the freedom that comes with owning your own future, not relying on the success of another company.
In my opinion, A 5e OGL would have to be bullet proof, AND a HUGE portion of the existing Pathfinder audience would have to want to convert before Paizo would switch. To the point that the choice would be between switching Pathfinder over or shutting down the project. An unlikely scenario, but possible.
Remember, a lot of what made Pathfinder successful as opposed to Fantasy Craft or other offerings was the production quality of the books, the tie-in products, the organized play campaign, and the World Setting it is based in. Not one element, but every element aligning at once.