Even with Current technology you can copy around 75 - 80 DVD's on to a small pocket size passport 320 GB usb disk drive -- just use Ulta ISO and copy the DVD image (works for copy protected DVD's, Dual layer etc etc as well).
Of course if you don't need the WHOLE ISO there are zillions of decent compression algorithms to extract and compress the data into much smaller packets so you could easily get say 150 - 200 DVD's on to one of these disks.
Now a 1TB pocket size disk would therefore be able to hold 300 (normal ISO copying) or up to 600 with data compression).
This is with CURRENT technology.
Actually as far as Blu Ray is concerned I'm very disappointed -- finding BD-RE (blu Ray re-writable disks) anywhere is a pain, they aren't that cheap and are MUCH MUCH slower than decent USB disk drives.
Watching Movies in blu ray is also a (comparative) disappointment -- there isn't a huge improvement from using a STANDARD DVD with a really good FULL HD UPSCALING DVD player. And I mean the upscaler has to be FULL HD and decent quality -- these DVD players are really cheap anyway now and also have hard discs in them for recording TV shows etc etc.
I'm looking forward to SS disks when the price is reasonable -- currently large capacity "classical" hard disks are still more cost effective byte for byte.
Blu Ray will remain a Niche medium - especially if you can download (legally) movies at high definition which in spite of the "Dinosaur Technology" the heads of the Movie and Music businesses still seem to be in will of course become commonplace in the next year or so.
When it comes to storage devices SONY seems to be behind the times
examples CD -- Philips etc - still in common use
DVD Panasonic, Toshiba, Philips still in common - but diminishing use
Betamax -- Sony Dead as the dodo
Minidisc -- Sony just about limping along - but only in very specific professional cases
Blu Ray-- Sony expensive and not a significant improvment in storage capacity compared with Hard disks, new SSD's etc.