The closed platform development benefits are not likely to improve performance anywhere close to over 2 times to fill in the gap between these two GPU solutions of the same architecture (likely even the same chip, specifically, give or take some minor differences such as disabled CUs and clock speed), let alone surpass it. General optimizations, as we've been seeing over the course of the previous console generation, benefit performance on both console and PC versions and unlike with anomalies such as the PS3's Cell processor, there is no learning curve for even PC developers to tackle with the PS4's standard PC-based architecture to lend any console-specific performance boosts as the platform ages.
This same discussion was had back when Nvidia's 8800 line was released. The 8800 GPUs had a similar performance advantage over the PS3 and 360 as crossfire 7970ms would have relative towards the PS4 and yet, the 8800GT, for example, commands the same performance advantage over the PS3 and 360 as it always did. The only specification I could see making a difference in relative performance between that laptop and the PS4's GPU would be VRAM utilization, given that crossfire 7970ms only have 2GBs of VRAM to work with, but at the same time, I question the PS4 GPU's capabilities to even utilize significantly more than that amount. That is a debatable aspect as are both its effect on relative performance and just how much, specifically, touted closed platform benefits will truly improve PS4 GPU performance. However, it is pretty much fact that closed platform development benefits will not allow a GPU to overpower a PC counterpart (of the same architecture, no less) with over 2x as much raw processing ability.