There's a lot of rumours floating around saying that Nintendo will reveal a new stationary console at E3 this year, and yesterday Game Informer added more fuel to the fire.
According to the magazine, inside sources have revealed to them that yes, Nintendo are working on a new machine that will finally support HD (something that the Wii lacks compared to Xbox 360 and PS3). While Game Informer say that they currently don't know "whether its graphics will be comparable to those on the Xbox 360 and PlayStation 3", Kotaku jumped into the fray saying that they have heard that the new console will actually be more powerful than both of the current HD-consoles.
That's more or less all the information available at this point, and Nintendo's official stance is of course that the company won't comment on rumour or speculation. If Game Informer's sources are correct, this new console will mark a shift in Nintendo's business philosophy though and that the company plans to embrace third party developers on a different level than they have with the Wii (something Satoru Iwata himself has criticized his company for and claims that they are already doing for the Nintendo 3DS).
No word on what brand the machine would carry or what kind of controls it will support. So you are free to speculate to your heart's content. E3 is getting closer and closer, so within two months we should know if there's a brand new console launching towards the end of 2012 or not.