The wiiU and the 3ds can speak to eachother via IP/ethernet already, so for cross-play you could just use that. The latency shouldn't be an issue if you have a 802.11n wireless network (depending if you have alot of wireless devices).
It is only if you want to display what the wiiU's rendering that you'd have to use it's wireless GPU output and have the appropriate interface on the 3ds (expansion card).

I suspect that Nintendo decided to bundle the Wii U tablet with the system because they saw a lot of value in DS-Wii connectivity but didn't believe that this functionality would ever be well supported by developers ... I'm not surprised they have patents on it, and I could see them using it in the future, but I think it is unlikely that it will get supported by most developers

The rumor is highly unlikley based on that part.
If the 3DS should render the graphics, you wouldn't need the special interface for it.

If it should only display the image and use the controls as input, how the hell does that image transfer directly to the screen? :S

As far as i know that cartridge slot does not have wires directly to the display.
If the purpose is to emulate a wiiU tablet its pretty much what it needs to do, and I would be amazed if it was possible to do with just a custom SD card and some software :D (MAKE IT HAPPEN! would be all over that shit from a technical standpoint)

Not just that, anyone looking at that cartridge thing and saying that it + the circle pad pro would be needed have never attached the CPP to a 3ds since it grips around the top and bottom of it and completely covers the cart port. anything even a mm over the normal cart size wouldn't fit.

Huh.. well that settles it.

It is not gonna be used for that exact purpose atleast, if it is still some truth to it.
Cause there is no way it is gonna work as the rumor states.

edit: god damn that thing is ugly.. glad i dont have it :P

It'll probably be bundled with Smash Bros 3DS.

And isn't this already confirmed by Nintendo?  Iwata said the 3DS and Wii U versions of Smash will work with one another, implying the 3DS be used as an optional Wii U controller for that game.

I think even Miyamoto has said in the past that though he can't talk any specifics, that 3DS could theoretically connect to Wii U similar to the GBA/ GCN connectivity.

it makes playing Resi evil so much better tho, I mean absolutely 1000 times more enjoyable a game with it, I have mgs3d to try out with it too but I got it wrapped up with a pre owned copy of Resi which set me back 15euros so I wasn't complaining :D weird how it connects to the 3ds tho... through the IR port, very odd device.

what the hell :P THATS what the IR port is for?!?!... well.. the japanese sure loves that IR..
not shitting you, EVERYTING has an IR port in japan.. and people don't get how they work still
cenario: phone-contact trade and the guy rammed his phone into mine like 1mm between them, i just smiled and thought "Its ok.. he dosn't know better..."

but anyway.. so this is something i should pick up? Gonna borrow the RE game from a friend in like 2 weeks.
Tried the demo though, and i thought it was ok with the 'standard' controls.. is it gonna be a mind blown experience?

I can see something coming to better link the 3DS and WiiU. That makes sense. I don't see it as described here and it definitely won't be a "second gamepad" exactly, as the screen isn't good enough to be a WiiU screen. The idea of the product coinciding with Smash Bros makes a lot of sense. I suspect a new model 3DS (like DS lite) with some better WiiU compatibility and an expansion pack for old systems is probably in the works. The synergy would boost both systems.

Not particullary contributing to the thread. But since the bolded seem to be a recurring subject, I'm going to ask... how so? I'm using gyro aiming and finding it much more enjoyable, precise and faster option than circle pad. Though sometimes I do find myself in akward positions after intense gunfight, I just cannot bring myself to use analog again.