(As an owner of a 350Z, Prius and also has a mother w/an Altima Hybrid...)
http://green.autoblog.com/2010/05/11...sion-of-the-z/
When I was at Tokyo Motor Show, I did see the li-ion pack pack for the Nissan Fuga (aka Infiniti M here) hybrid and it was MUCH smaller than the one you'd find in the back of a Prius or Altima Hybrid. It's pictured at http://www.autoblog.com/photos/tokyo...ybrid/#2384477. The picture from the other side gives a weird perspective and makes it look quite large.

I think it's more logical they'd use the above RWD system developed in house from the start or some mild hybrid start-stop system than something suggested by someone who doesn't know much about the FWD Altima Hybrid in the comments.
I doubt Carlos Ghosn wants to pay Toyota even more money and develop this one off car somehow modifying a FWD powertrain to work in a RWD application, considering the tiny quantities in which the Z sells.

They've been demoing and talking about their RWD system for awhile. Examples at http://green.autoblog.com/2008/02/16...finitis-first/ http://jalopnik.com/399942/nissan-re...uel-cell-stack and http://www.insideline.com/infiniti/g...35-hybrid.html.

(For those who don't know, the Altima Hybrid uses technology and many/all hybrid components licensed from Toyota and utilizes a power split device (http://eahart.com/prius/psd/) form of CVT. It's likely closest to the Camry Hybrid. When I was at the San Francisco Auto Show years ago, the plastic cover on the Altima Hybrid's inverter was detached. If you moved it over a little, you'd see a Toyota barcode and part # on it. )

Let the hybrid bashing begin... (ducking for cover)

 

if they can match the performance of the 370z but with hybrid capabilities, im all for it. The one thing i wouldn't think would be good because of how would the performance person get more power from aftermarket parts? first mod i think would be tune in congution(i think i spelled that wrong :/ ) with every aftermarket park. I dont know to much about hybrid but what i do know computers are are controlling more and more of the car then they use to. just my .02cents on the subject.

 

fair points, but i think modding a hybrid Z would be counter-intuitive; almost all mods increase power while decreasing efficiency. I'd guess that most people willing to buy a hybrid version of a sports coupe probably arent concerned with modifying it.

 

This looks like the same unsubstantiated rumor that came up almost exactly one year ago...

https://my350z.com/forum/2009-370z/4...or-2011-a.html

Here we are a year later and there has been no verification or corroboration of that rumor, nothing tied to a Nissan source, no hint from Nissan itself. They must be keeping it buried really deep, unlike the leaks that foretold the return of the Z or the arrival of the GTR.

I'm sure a hybrid or electric Z will certainly blow the auto industry away and virtually corner the market for Nissan. You know how all those greenies are dying to have a impracticle, 2-seater sports car. (I'm being extremely facetious for those that can't tell).