Does anyone know if WoTC has an approximate release date for D&D Next?
Almost certainly. It's very doubtful they would have started on this process without a notion of how much it would cost, and that cost is directly related to the length of time involved.
They have not, however, made the date public.
Does anyone have an educated guess?
GenCon 2014 seems to be the most popular guess. It makes a certain amount of sense - they'll no doubt be doing a massive "40th Anniversary" thing at that con, so releasing then makes sense.
However, an alternate possibility is that they release a month or two
before GenCon, allowing them to get the big push for a new edition and then a second big push for the anniversary. Plus, it allows for more people to actually be playing the game at the Con.
It seems like they are taking a LOOOOONG time. The transition from 3.5e-->4e didn't take this long. Did the transition from 2e-->3e?
IIRC, the
public transition from 3e -> 4e was about 10 months (from GenCon to the following June), but they'd been working on the new edition for some time in the background. Publicly, the transition from 2nd Ed to 3e took about a year (Dragon did "Countdown" articles along the way), but again, WotC were probably working on it in the background from the moment they acquired D&D.
Personally, I'm glad they're taking the time. Although I'd very much like to have the new books and the new system to admire, we're more likely to get a good product if they wait until it's ready. I just hope they don't get rushed into a release by financial realities at Hasbro.