I believe Brandon plans his writing schedule in the next few years to be: Stormlight Archive, Stormlight Archive, Something Else, Stormlight Archive, Stormlight Archive, Something Else. Etc. That's one book per year (of course Wheel of Time will be concurrent for the next two years), so the earliest Brandon will put out Nightblood is 2012. He might write the sequel to Elantris first, but he may want that to come out in 2015 for Elantris's 10-year anniversary. Of course, he may want to write something else instead like The Silence Divine to come out in 2012, meaning Nightblood might not come until 2018. However, I think right now that 2012 is the most likely date until something changes. (He may also be able to write faster once Wheel of Time is done, but that extra time may go to non-adult projects like Scribbler. He'll probably stick to one Brandon Sanderson adult fantasy book per year.)
Of course, if he releases Nightblood chapter by chapter in draft form the same way he released Warbreaker, then you will get to see it sooner. He mentioned before that he was planning to do that, but that was even before the WoT news broke and things may very well have changed since then.
As for the special edition ebook & annotations, Tor is working on it and last I heard they wanted to release it "soon." The annotations won't start going up on Brandon's website for months yet, since the Hero of Ages annotations just started.