The speculation is in on just what the model could be. A large number of people are assuming it will be a marine, but really only time will tell.
The pic above is a golden daemon silver award by Greg Smalling back in 2007.
Please take this with a good amount of salt due to any anniversary model release is still a good ways out.
I was told today that there is going to be a 40k 25th Anniversary Model released on the 25th of February - like Harry the Hammer it will only be available for that weekend and will be in finecast.
Sadly I have no more details beyond that, so if you have an idea of what it is let me know! I am most curious indeed, especially given the nostalgic throwback of the Games Day model this year...