My guess is that 2.2 will be coming "sooner" rather than later and it will include the Voice Chat and sound engine update and the posted API/game changes.
2.3 will be the first content update (zul'aman) other than the Brewfest addition.
Beyond that it's total speculation, since this
is Blizzard we're talking about.
PS: My computer blew up so that's why I haven't been around as much lately /cry