I forget where, but I saw an interview with Bill Ropier saying that they will not use the B.net system, they are developing a new system.
This is good because they've learned a lot from B.net over the years, and they can put that knowledge to good use.
However, I am still going to wait for reviews and such before I decide to play WoW - Even though it's Blizzard, and I feel they're gonna do a great job, it's a MMORPG, and MMORPGs are a different realm, a different beast -- many games are ruined in my opinion by going to the MMORPG style.