Blizzard has confirmed in their latest Blizzchat session with fans that they are aiming to get the Starcraft II beta into the hands of Mac users by April.
"We are currently working on a Mac version of the beta and hope to release it sometime in April."
So there it is. Mac users need only hang tight for one more month and the zerg rushes can begin. Among other questions posed during the Q&A were if Blizzard had any plans for an open beta which, unfortunately, there are none at this point.