updated 01:45 pm EDT, Tue April 13, 2010
All MacBooks may get HDMI connector soon
(Updated with Apple stance) Apple in its launch of the new MacBook Pro today put out hints that it will more officially support HDMI soon. The video options in its specs list show the option of HDMI output using an official "Mini DisplayPort to HDMI Adapter" despite Apple having made no mention of such an adapter itself. A search of the online Apple store doesn't show any adapters of the kind, whether made by Apple or anyone else.
Third-party adapters have existed before, including those from Kanex, StarTech and TeleAdapt, but these have never had official recognition from Apple. The DisplayPort spec is technically compatible with HDMI but doesn't supply HDMI's usual audio without a secondary connection.
Any plans for an adapter may indirectly support rumors of a Mac mini with HDMI as it would show Apple taking a more active interest in TV output. Users to date have often run the Mac mini and MacBooks through their TVs as unofficial home theater PCs but have often had imperfect resolution support. HDMI is now a fairly common output option on Windows notebooks with sufficiently fast graphics hardware.
Update: Apple has said it doesn't currently have plans to make its own miniDP-to-HDMI adapter.