It's kind of like the old days when "stereo" was the new thing. If it wasn't recorded in stereo, it ain't going to play in stereo.
Same with high def. If it wasn't taped in high def, you ain't going to see high def. Be patient, after the February deadline and all transmitting stations go all digital, the high def program content will increase. I would suspect that all prime time programs will be in high def, but I doubt many daytime programs will be, at least for the short term.
As production companies shed their old technology equipment for new, we will see almost all high def, though it could take a year or two.
Wayner