It seems impossible that sports right fees will just increase forever and forever; people once thought the same thing about housing. However, along with "live" reality TV shows, they do seem to be the most immune to DVR and delayed viewing. I could see where some of the rights packages come in at equal or slightly lower than projections.
Of course, I also think the eventual end game for most of the established media rights owners - whether we're talking the past library of MLB games or all of NBC's "Must See TV" and late night programs - is having their own digital media service, a la the WWE Network. Anything that isn't big enough to stand on its own will ally itself with one of the big media servers, until we eventually get some mergers and fewer companies... Until the next technological innovation makes the process repeat all over again.