The GP104 is the successor to the GM204 GPU and the shipping records indicate it has a 37.5mm x 37.5mm BGA package, slightly smaller than the 40mmx40mm package of the GM204. Additionally, we also learn that the ship uses 2152 pins, versus 1745 for the GM204.
It is believed that the GP104 may feature GDDR5X memory, and that HBM2 may be reserved for the GP100, the big flagship version of Pascal. GP100 is believed to have a 55mmx55mm package, quite a bit larger than the GM200's package due to the inclusion of HBM2.
It does seem that both GP100 and GP104 will be smaller GPUs than GM200 and GM204 respectively. This is the first branch of FinFET GPUs from NVIDIA, so the time for much higher performance gains (like we had with GM200 compared to GK104) will come later. First Pascal GPUs just need to be faster and more efficient. Of course these are just the first steps in FinFET architecture, it will take time to develop faster graphics cards, but I’m quite sure FinFET will stick around for a while just like 28nm did, so there is no rush.
Additionally, one of the parts listed below mentions watercooling so there's speculation that NVIDIA is planning watercooled versions of its GP104 but we don't have any further details at the moment.
AMD is also shipping around its next-gen GPUs, more about that in the next post.