Couldn't possibly have anything to do with their six month lead time in the market would it?
So what is the point of bringing up those steam numbers?
To show that from a universe of around 25 million accounts (most recent numbers known, I believe), 6.18% or 1,545,000 users have DX11 capable GPUs, and from those 40.06% or 618,927 have 57xx cards, another 39.72% or 613,674 have 58xx series cards and 45,268 have 5970, while there are 29,200 users with GTX 480 and and 27,964 have GTX 470?
Ah, wait is to show that the number of 5800/5700 are dwindling.
But are they?
Well, we don't know how many new accounts are in there, but we know how much the DX 11 share grew and we know the DX 11 share was 5.58%, so lets assume similar number of accounts.
So while in May there were 1,545,000 DX 11 GPUs in April they were 1,395,000 (5.58% of a 25 million universe).
So in April the 57xx represented 43.46% of the DX 11 share or 606,267. In May the 57xx DX 11 share decreased 3.40% but the number of units is 618,927 an increase of over 12,000.
In April the 58xx series represented 41.85% of the DX 11 share with a total of 583,807 units. In May while the share decrease the number of total units increased by 29,867 units.
So by how many units did GTX 480 and GTX 470 grew?
In April there was 6,138 GTX 480 cards on steam. So GTX 480 units increased by 23,062.
GTX 470 in April 9,067 so an increase of 18,887.
So today, 8 months after the 5800 series is out, the market is going 45 5800/5900 cards to 55 GTX470/480.
How many months is it going to take to close that 600,000 unit gap between 5800+5900 and GTX480+GTX470?
If anything, the steam numbers do say "First to market is critical!".
EDIT: And this pretty much the best setting for NVIDIA (well the best is if number accounts is going down) - if accounts numbers go up, due to disparity in total numbers, ATi will be selling more cards.