These things take time according to Gabe so I would be suggesting this should have been in GT6 and now since PD doesnt seem to care too much about the VGT program this Mazda is unlilkely to ever make it to GTS.
It's not a Vision GT, otherwise it would literally be called Vision Gran Turismo like all the rest and had a trailer and an announcement on the GT website by now like literally all the Vision GT cars.