The Perils of High Definition Television

I recently saw this image on TV:

Note, it is a high definition segment (of Thomas and Friends), embedded on a low-definition program, broadcast on a high-definition digital television channel (Twin Cities Public Television, TPT-2), filtered through the low-definition analog channels of my cable-TV system (Comcast) onto a low-definition television (Sharp). The picture was taken with an iPhone.

This is progress. If there is a new generation of high definition television, will my programs, to retain backward compatibility, be even smaller, until eventually it is only a pixel on my screen?