I think that will soon become reality. It's already happening in the SatTV world where DISH is now offering "free" HD service (not programming but the ability to receive HD). DirecTV has countered by matching that for new customers and also existing customers (6 mos or longer) that ask. Existing customer only get 24 mos. for "free," but I think in two years no one is going to be able to charge extra for "HD." It will have to be embedded in the price.
Also DirecTV's NFL (US Football) Sunday Ticket previous required a $100 a la carte package to get the games in HD. This season that package is not included in the regular one at no extra cost. Instead they are charging $50 extra if you want to view the games on the iPhone. I'm not sure how many suckers they are going to get for $50. I'll just watch w/ my sling app.