I think that battle.net supporting 8 wows is the biggest reason for supporting multiboxing. I mean, what possible reason would 8 accounts be used for? I can see a regular player having 2, maybe 3 accounts, and a few hardcore having 4.

Wow looks to be on the end of it's cycle. It's got another expansion or two, but IMO, it's only downhill from here. The only saving grace is that Titan was pushed back, so they're gonna have to do something to keep up the subscriptions, so hopefully blizzcon 2013 reveals something interesting.