Blue-ray and HD-DVD: I think DVD is here for the long term
Right now, a consumer can buy a DVD player for under $40. Many "high definition" TV sets are really just S-video quality that downsample high definition to the lower display resolution.
DVD was a great improvement over VHS tapes, but I just don't think that the new formats are going to catch on until the players are cheap and the media costs come way down. Also, just think about the mess in consumer electronics stores having to stock so many options.
My Dad is an amateur movie maker - he combines live high definition video with lots of computer generated material. He uses a high end Mac, and enjoys working with the new high definition formats. He runs cables from his study to his high definition TV in the living room, so he does not have to burn media. Anyway, he has a lot of fun, but he is not the average consumer. I think that for several years consumers will stick with DVDs.