MacBidouille claims that Apple will be supporting some professional video cards in Panther. The list includes NVidia's Quadro 2, Quadro 4 and ATI's Fire GL 8700, GL 8800, GL2, and GL4.
Of additional note, they claim that certain Select and Premier developers have started receiving PowerMac G5 orders. Being so far ahead of the general population, it's unclear how accurate this report is. No independent confirmation available.