There is also the old DX 35mm 1.8 G,,,
Similar size and design as a 50mm 1.8 G,,,
I don't think there is much to 'save' in a DX fixed focal length 'optimized' design approach compared to 'just' designing it as FX, the gearbox and SWM motor, mount, contact bloc and electronics, mirror box design - all optimized for FX - so I think we will see very very few DX primes, it simply doesn't make any sense to do it,,, IMHO