Well, hey now. The folks at vr-zone got their hands on a picture of MSI's GeForce GTX 660. This fifth GK104 based part might be introduced at next week's Computex:
While the image of the board is obviously photoshopped (the lower part of the bracket is not present, the heatsink has a six-pin connector slapped on top), we checked with our sources and the product appears to be legit. The highlighted single six-pin connector on the heatsink was positioned there to highlight that the board cannot pull more than 150 Watts, which the author of the leaked image made sure off.
The photo is courtesy of vrzone.