I don't think streaming (guaranteed to play @ high bitrates and resolutions WHILE downloading) content will attain great market share. If Blu-Ray stumbles then downloadable
HD content may take off in the form of content delivered straight to the hard drives of DVRs, consoles and proprietary set-top boxes.
Maybe you will be able to watch some of it whilst it's still downloading. I dunno, it seems to me though that at least SOME form of downloaded and locally-stored HD content will be the format of choice. I just don't see anyone committing to being able to satisfy bandwidth requirements for true streaming. ... and then on the other hand maybe I don't know enough about current internet vs. cable tv data throughput.