as version 5 is the newest version, yes. if you already own Logic 5 Platinum, just head over to Emagic's site and download the OS X upgrade. Cubase SX and Digital Performer will be arriving to OS X later on, but I like Logic myself anyways.
Actually only Logic Platinum and Logic Gold are currently avail for OSX at the moment. I don't know about emagic's other software tho, Sounddiver, Exs24. etc....
G