Nintendo owns patents on Holographic storage, so we don't know if they finally matured the tech enough to make it cheap. But this BRD rumor first popped up in 2009 for the release of a WiiHD in 2010, and now it pops up again with the news of a new N system, so I'd take it with a grain of salt.
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As far as the casual thing and BC, I sorta explained how it was for both groups and how both groups may look at it.
Casuals will think that the hardware they just bought a few years ago is working fine and how they don't need anything new, and if they do think about upgrading, they will think about the 100's of $$$ they've spent on all the software sitting on their shelves and if they will still be able to use any of it. There would have to be something in the new system to make them take the leap, and it will have to be especially good if they want everyone to abandon their current system and all it's software.
As far as the core, current Wii owners are gonna want their current software to work, and might go back and rummage through the bargain bins for anything they skipped over. People that Never owned a Wii because they never rationalized owning the system because there was "No Good Software" can now rummage through the back catalog for cheap gems that they skipped over (Punchout, TLS, Xeno, etc etc).
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And if there is a sizeable HDD of some sort, I'm willing to bet that GC will move to Virtual Console, I actually wouldn't be surprised if some Wii games showed up on VC too, depending on how powerful the new system is.
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Something else I was gonna post last night(my computer reset and I can't remember where the links are now) was actually from a little over a month ago. An AMD employee was talking about how he was on the team that was working on a new chip for a next generation console due for release at the end of 2012. He said this back in the beginning of march. It's an AMD Fusion based design which is combined CPU/GPU upto 4cores @ 28nm and if I remember correctly, is the same type of design AMD did for MS with the Xbox Slim to eliminate the RRoD for Slim models.
It's assumed that this work was for MS and I wouldn't be surprised if MS was planning for 2012 all along. The 360 did come out in 2005 after all and Kinect came out in 2010, so 2 full years for Kinect before a new system seems reasonable. But what if this is actually a Nintendo chip?
quad core CPU/GPU combo and all RAM would be a shared pool since both chips are on the same chip.
R&D for a custom CPU/GPU combo would be expensive, but the chip should be significantly cheaper to fab once it's combined than if they were separate.