My mail is kept in Thunderbird on my PC. As are my photos - do you really trust everything to Google/etc? Plus, it would take nearly 2 days to download a Blu-ray quality movie to my PC on my current net connection and I can't see that improving very quickly.
I wouldn't even try to predicate Blu-ray sales compared to DVD sales, but I believe Blu-ray will take over. It might be the last physical media to do so, in much the same way as CDs were the last audio physical media to sell in big numbers - SACD, DVD-A and Vinyl are niche formats and I could see Blu-ray's successor being the same.
I'm also in no great hurry to ever watch any movie on a pocket sized screen, but that's a different kettle of pandas.
I saw my first ever HD-DVDs for sale today too. Miami Vice for £15. I was tempted, my player plays everything, but if I ever want to play it elsewhere or after this drive has gone, I'd be SOL.