HD 3D, then ultra high HD 3D, then extra ultra HD 3D.
There won't be any discernible difference in video quality, but it will be marketed as such with a higher price tag, so consumers will believe it's better......and buy it.
But on a lighter note, look for more innovation in convex screens in the larger models.....like 72" and up. You can't get more in detail than 3D, but improvements can be made in how that 3D is viewed. Different angles and all.