Perhaps the photographer is sending us a coded message in the EXIF data. The pic is 25.2 megapixels, why not 25 exactly? Because the new camera has 25 megapixels and is .2 or version ii, therefore it is code for 7D mk ii. 
I really thought this had been left behind, which would have been a good thing. But, since not...
Do you suppose it really might just have been actually taken with a 1Ds III like Stephen Oachs uses, and the 6144x4096 image size is just a quirk of the regex tool?
No, I guess that's not possible. Certainly, if that were the case, other photos wouldn't show up with that resolution, either. Photo's like
this set on sumgmug, or
this set, or
this set. Below is the SmugMug info from one in the yachting set. Note the date.
Wait, maybe you're right...and Canon has been sharing this prototype 5DIII since 2008 (wasn't that when the 5DII came out?), and sharing it with pretty much anyone who asked nicely and promised with their hand on a Gutenberg comic book or a pinky swear not to leak photos taken with it.