I predict Disney will release them on the 40th anniversary in 2017. As far as anyone has indicated there isn't some special contract thing where they are forbidden to release the originals. Even Lucas, a year or two ago, said something about schedules and budgets holding a re-release up--which is absurd of course, but in hindsight maybe he was already thinking about selling the series and simply wanted someone else to pay and deal with it.

The only thing I can think of holding up a 2017 release is the Fox deal. I'm not sure how future home video deals will be, but Fox's distribution rights will lapse in 2020 but for A New Hope I think they might own the rights in perpetuity (is that the word?). There's some confusion on that status. It would make things like a box set potentially a bit complex, legally. But Disney knows that will happen, no matter what, so I'm sure they'll work out something, if they haven't already.

So, that's my prediction. 2017. It would dovetail with the 3D releases, since they will end in 2016. But I wouldn't stop working as though we know that might happen, as it could easily not. But with Lucas out of the way it will definitely be soon. He sold the films entirely so I guess he doesn't really care anymore. That also means no more SE updates. I guess Disney could do one themselves but the only time I can think of a company making an updated version of the film without the director (or the directors notes) is Night of the Living Dead, and that totally backfired (and sucked).

Also, I think Disney will follow Lucasfilm's lead when it comes to fan projects. The Star Wars machine is simply too big to stop now and Disney has been pretty relaxed when it comes to Marvel fan projects.