For many moons, "when it's done" was the only release date Blizzard would give for Diablo III--comforting, but slightly frustrating. However, now it's "targeting" a Q2 launch, Blizzard is preparing to ship the game before it's done, cutting out the PvP Arena mode to fix it up and patch it in after launch.
Diablo III game director Jay Wilson wrote in a blog post, "We wanted to let you know that we've made the difficult decision to hold back the PvP Arena system and release it in a patch following the game's launch."
"After a lot of consideration and discussion, we ultimately felt that delaying the whole game purely for PvP would just be punishing to everyone who's waiting to enjoy the campaign and core solo/co-op content, all of which is just about complete."
We got to play Arena PvP way back at BlizzCon in October 2010, and were pretty pleased with it, but evidently it's still not up to Blizzard's standards.
When PvP does "ultimately" launch, Wilson wrote, "it will add multiple Arena maps with themed locations and layouts, PvP-centric achievements, and a matchmaking system," along with a "personal progression system."