I read in another post here that there are three mux streams available on DVB-T (owned by different entities), and that each mux has a fixed capacity of about 24 megabits/sec. Is it fair to say that as more channels are added over time that the picture quality of the individual channels will degrade, given that the bandwidth capacity is pretty much fixed and the only way to add new ones is to lower the bitrate of existing ones? Or perhaps are the transmitters not currently using all available capacity?

The reason I ask is that I've read forums commenting on overseas providers who say the HD transmissions of today run at a fraction of the bitrate they did a few years ago because of the proliferation of new HD channels crowding the same number of transmitters. Will the same thing eventually happen here?