Holographic hard drives may be at least two decades off, but holographic
discs are one decade off at the most. They already have disc drives (and discs) available to the public.
They're just really expensive ($18000 a drive, $180 a disc).
And the only reason why DVD's are still mainstream is because blu-ray hasn't developed enough. It's still relatively new. The same thing happened when DVD's came in to replace VHS. But even though blu-ray will overtake DVD's at some point and become the preferred storage medium for movies and stuff, it's reign will only last a few years as holo-discs will come in and slowly phase blu-ray out. Just as DVD's did to VHS, and as blu-ray will likely do in the near future to DVD's.
And I'm probably wrong, but Sony still holds the patent for blu-ray, which makes developing high quality blu-ray players difficult for other companies.
But if you want something that's more than two decades off, take a look at
this. 5 EXABYTES (5,242,880 Terrabytes. Don't even thing of asking me for that in gigabytes) of storage PER DISC.
Mind blowing, but no where near being publicly available. Of course, I believe there's about 160EB of data on the internet, so you'd need 32 of them to store all of the world's data, but that's still nut-numbingly amazing.
Anyway, this is about Nintendo finally getting serious about storage. So lets talk about that.