Anybody can make a mock-up in Photoshop, fullscreen it on a monitor and take a photograph of said monitor. There aren't any real indicators that demonstrate hoax or otherwise. I highly doubt the veracity of that image.
On another note, even if it's fake, the mention of portability from PC and Xbox 360 has some logic behind it - easier porting would make for cheaper development costs compared to developing for the PS3 platform.
If the rumours are true (regarding the power of the system and Nintendo's aim for the product), I wonder if the company will be able to sway and win back the gamers they alienated with the Wii.