as a purveyor of high-definition television sources, I am somewhat concerned by the migration to this new standard of compression. Since the signal I received is coming from my cable company, the picture I am receiving is already somewhat compromised. Will this new codec result in a picture that is less clear and vibrant and the one I am seeing now?

MPEG-4 is a more efficient codec than MPEG-2, which is probably what your cable company has been/is using, if you are getting a digital package. So unless your cable company significantly increases the number of channels after switching to MPEG-4 your picture quality should stay at least about the same, or even increase.