I knew the larger capacity disks have been around, I couldn't recall the date they appeared. I also recall mention of 100GB, and possibly 200GB will be produced at some future date.Dual Layer BDs have actually been around for a very long time, and been used to deliver many, many movies (in fact, most BD movies take up way more than the 23.5 GB you can fit on a single layer, with extras and the various audio tracks, etc.) and games (I can think of at least three high-profile games that ran well into the second layer and sold millions). And when you start considering, say, the Lord of the Rings films in their extended versions, it quickly becomes easy to run over the 47 GB you'll get out of a DL BD.
Since then, they've managed to boost single layers to 33.4 GB and they've figured out how to cram something like 4-8 extra layers on a disc, readable by existing hardware with just firmware updates.
Somehow, I'm willing to bet that there won't be a competing optical media format for some time, and when it arrives it'll have an uphill battle against Blu-ray, which is already entrenched.
Aside from shipping hard drives or SD cards with the media on them, there's no replacement for high resolution video (Don't forget, 3D will require more space and there will be more resolution boosts upcoming) for consumer delivery.
The bandwidth just isn't there yet, especially in America. I envy Hong Kong's 100 Mbps symmetrical connections for $15/mo, because I'm paying $60/mo for 15/5 on FiOS. I feel ripped off.
But when I was thinking on a movie on 25GB disks, it would be "bare bones"; basic movie, no additional content to make sure it fit and would play on any BD Player (firmware updates may not be consistent enough from manufacturer to manufacturer, causing a larger capacity disk to not work properly on some equipment = unwatchable).
Then when I see other disks for the additional content, it seemed to fit with that logic. (I don't have a BR reader/burner in a computer, just a BD Player for the HD set, so I haven't been able to check the disks I own for size or filled capacity).
I agree, it will be BD for sometime yet, as with the discontinuation of HD-DVD, no one else would try.
Bandwidth is the real issue, as that's what will eventually replace physical media for 1080P and future specifications (3D, higher resolutions,...). But as the US is slow to upgrade and adopt newer tech (companies want to make every cent possible by dragging it out and attempting to get government projects to foot at least part of the bill), that's going to be awhile.