No specific numbers = No argument ...
He just showed them:
That share is quite small then.
The downhill trend is also quite obvious. When the HD7900 alone have sold around the same as the entire 200 series. Including R9 and R7. Not to mention the obvious missing 300 series that haven't even reached ~0.16% of the installed base to show.
And you are right, developers do care about market share. And the top product is GTX970 with ~6 million users on steam alone. Followed by GTX960 and GTX750TI with ~4 million each. That's the top 3 discrete cards.
And yes, the survey is opt-in or whatever, but I don't think you can ignore steam hardware survey numbers at this point.
The GTX 970 is an extremely popular GPU, but I don't think it's intelligent to target Maxwell (or any specific architecture), because I find it extremely hard to believe that a majority of gamers are on Maxwell. We're spread out between all different GPUs, games should be GPU architecture neutral or try to.
Yes, I do expect newer games to use new features (like Async Compute), but we expect that. We dont' expect a GTX 780Ti/780 to drop performance relative to AMD counterparrts, ESPECIALLY in Nvidia games. That's silly as anything if I buy an NVidia GPU and the only way to reap the benefits is to always be on the fastest newest card.