Wow, go away to law school for a year and all of a sudden we have 5e now?!!!
You see now why you're never allowed to leave again? This is why we can't have nice things!
(1) When does it come out?
No release date yet. They're doing organized massive playtests to make sure every gamer out there loves it completely before trying to sell it.
(2) Are any of you going to run ENWorld pbp 5e games?
DarwinOfMind is running one right now, based on the current playtest iteration. Not sure if he's still taking players though. At least the thread can be ogled in an unseemly fashion.
(3) What are the significant rules/class/magic updates in 5e?
I'll tell you what I've heard, since I'm not personally familiar with the playtest documents.
First, Vancian magic is back in, though it may not be the only magic system possible.
Second, "at-will" spellcasting is in as well, by means of special feats available to mages (maybe clerics/divine casters as well?) that give them access to such spells.
There are still distinct 'wizard' and 'sorceror' classes, but I have no information on what makes the distinction. From some of the descriptions I've read, bloodlines still seem to be part of what defines a sorceror though.