Honestly guys its about necessity more so than anything else.
You CANNOT have a physical disk drive on a handheld, without it being gigant and powerhungry.

I think the idea of haveing the same "medium" for both the handheld and the consol, is brilliant.

"take your games with you on the go".

(no compromises, its the same game, on the handheld as on the consol. To me thats a huge selling point)

(as a consumer you wont have to buy differnt versions of the same game, if you want to play on one or the other, or have to choose between them)

***** OBS : brillient idea = make it so you can share "save game data" between your consol and handheld... BOOOOOOM.

You can now play the same game at home in front of a tv, then contiune on your handheld from the exact same place you left off, before leaveing for work/school ect.

Developers will love you for it:
You wont have to develop the game for the consol and then port it to the handheld.

(double the market penetration, both handheld and consol sales for 1 game)

You wont have to have 2 productions for the same game.
(mass production => cheaper than haveing 2 productions running for every game made for your system.

As far as I can remember Iwata's statements about their future consoles he's said they're aiming for a unified OS, something akin to iOS where you have the iPone and iPad. Did he really indicate that the devices would share the same games? Let's remember that iPhones and iPads both have their own exclusives....

He didn't but the were whispers or some kind of patent of a concept called Fusion with one hardware unit accomdating both Handheld and home markets, the IOS style concept was mentioned by him. 

Some yet nonexisiting form factor.

If the portable console should read the same cartridges: Somewhat bigger than SD cards cards overall, but very different form ( think about GBA cartridges flattened to SD card thickness just as an example; such a broad format would allow more connectors on the cards and along with it, a higher transer rate). If not, a more classical cartridge could be used with more space for later extensions and more connectors for even more transfer speed, but at a higher production cost.

This would give Nintendo several advantages: Custom-made for their needs, full product control, and along with these, a physical copy protection as there are no readers for them exept the consoles and the Software Development Kits (that doesn't mean no other copy protection would be needed, it would just be another layer of protection).

@exdeath: It's true that the fastest SD cards also have a higher transfer speed than Blu-Ray discs, but these SDXC cards are also relatively expensive in production. That's why I said "for the most part". Also, a theoretical 20x Speed Blu-Ray drive would be just as fast.

In any case, these transfer speeds are very slow and not really on par with the needs of video games, where a 200+ MB/s Transfer speed would be very useful. For comparision: SATA III has a theoretical maximum of 750 MB/s, SATA-Express in the latest Intel-PCs almost reach 2GB/s, USB 3.0 theoretically could reach 625 MB/s, double that for the new 3.1 standard (USB however does loose quite a bit on their overhead), so 90 MB/s are ridicilously small to the capabilities of modern standards

SATA 6G is 550-600 MB sec in practice.  Address, interrupt, and control data are now headers and packets, eg, everything is data in a serial bus.  There is also 8/10 encoding of the data to keep in mind.

Yeah 90 MB/sec is nothing (I use 2.5 GB/sec SSD arrays and 10 gigabit Infiniband)  but its still 1000x faster than a disc when you start seeking.  Though it's probably not that important on a console where the game is built from ground up to stream sequentially off the media and not like a PC where theres lots of random I/O and misc. scanning and searching going on all the time.

Sata Express needs to be a thing faster.  SATA 6g is such a bottleneck and the only way to get around is it multiple channels.

The idea is actually very good, Rol.
Seems like a very pragmatic proposition and a cheap one at that, too (something that Nintendo likes).

I think the only thing against it really is 3rd parties.

It's true that a lot of devs have dismissed Nintendo's consoles, but we can't overlook the fact that Nintendo's strategy for it's consoles - especially the home console - was nowhere near insync with 3rd parties of doing business.
3rd parties strategy was, although, perfectly insync with Sony and MS - or vice-versa.

Now,we know that Nintendo's strategy aside, companies like Ubisoft, Activision and some japanese companies will be willing to at least try and support at first.
And japanes devs won't hesitate to support Fusion even if because of the handheld market.
How will that work for them?

Imagining now that Nintendo's strategy is to have as much classic Nintendo titles as 3rd party-like titles.
That will create a market for 3rd parties if Nintendo is successful; 3rd parties will see that and will want to join in. Do they have the right conditions to do that or lack of space will stop them?

Nintendo needs to take care of what will happen but also of what can happen.
Doing things just for Nintendo's liking is what they have been doing for generations and look what that got them.

Yeah I know of the limitations of SATA, that's why I said theoretical maximum. It's enough for HDDs but wholefully inedequate for SSDs which get limited by it's narrow bandwith.

SATA express is based on PCI-Express, so with PCIE 4.0, almost 4 GB/s would be possible. That should suffice for most SSDs.

I hope more the producers will soon start using PCI Express, still can't find SSDs for this connection despite it's advantages over SATA 6G

Such a good idea that it seems like a no-brainer to me. 

Saw a post about backwards compatibility...  Was it nice for the GBA, DS, 3DS, Wii and Wii U?  Yes, but if it holds them back on their next systems then I say screw it.  They just need to add ability to transfer your VC collection (Wii, Wii U eshop and 3DS eshop VC games) to the new systems.  WiiWare and other games can stay on whatever system they are on.  Sony and Microsoft didn't allow transfers of their eshop games to their new consoles and there wasn't too much uproar.  I'm sure it would be different in regards to Nintendo though.

I still believe in the phisical media. The industry still are developing tecnology for disc based medias, and new formats are possible with great gains in storage capacity and speed.
But this only time will tell...

I was talking about people who were sugesting to not have a HDD of any kind, in the system.