I know alot of people say to rewash after claying and I can understand why. It's possible that you loosened dirt with the clay bar but didn't pick it all up. Therefore a re-wash will be sure to leave you with a completely clean surface.
I think it also depends on what you are going to do after you clay. If you plan on waxing or sealing immediately after, I would at least use a QD, if not a complete wash. Remember surface prep is 99% of the shine. If you're waxing over dirt, it won't look as good.
With that said, if you plan to use a polish or pre-wax cleaner after claying, I would say you don't need to wash or even QD.
Me personally, my full detail process includes a wash, clay, polish (or pre-wax cleaner depending on the condition), QD, seal/glaze, QD, wax, QD.
The multiple QD steps may be overkill but it makes me feel better. Some of the products I use create a lot of dust when buffing so I like to use a QD in between steps to ensure that the surface is clean before the next step. Also, dust particles in the air can settle on your car, especially if you're detailing in a driveway that is close to the street.
Just tell yourself before using waxes or sealants, the surface can NEVER be too clean.