I don't know the exact, official status of the Transporter but you're right, it is missing from the product line up now. However it was doomed to go out at some point since the visual display modules used in it were no longer being manufactured.
I'm assuming they have some in inventory for warranty service but probably not enough to continue new production.
I auditioned a Transporter a few years back and ended up with a SB3 and a Lavry DAC. I thought the audio performance was equal, though I know others disagree. I've since added a Touch and am very pleased with the audio quality.