Given that the Eighth Doctor has already been shown onscreen in the likes of The Next Doctor, the idea of an incarnation who The Doctor has blanked out and isn't entitled to be called The Doctor isn't really applicable to him. I would love to see McGann back but the Hurt incarnation doesn't seem to work with a previously known Doctor.
He wouldn't be completely forgotten like Hurt, he'd just be "Here's the Sixth Doctor, wacky clothes bla bla bla, here's the seventh doctor, the intellectual type near the end, oh, and here's the eight doctor.....
andway, the ninth doctor who wore bla bla bla..."
Plus anything that happened in his eighth incarnation is never really mentioned much.