No new car as far as I know. I doubt there has been any DLC's as well (at least I haven't seen any for GT6). It's a shame because I was really wishing to drive the McLaren P1 in GT6 someday. Probably will be in GTSports or GT7.
It's not necessarily dying, at least not from my point of view. It may be because they have been working on GTSports for a while. But yes, I agree, it's a shame there have been no DLC car.