According to a TIME magazine interview with Sony's global game development boss, Shawn Layden, every one-in-five PS4s sold at the moment is a PS4 Pro.
While Sony might not have released the PS4 Pro without having a good idea the upgraded version of the console would sell, it must still have been a gamble to release (a gamble that Microsoft is due to repeat, with the likely imminent announcement of the Xbox Scorpio). And so, for Sony, the definite fact that consumers are willing to put the extra buck aside for sharper graphics and more frames is a validation they must be happy to have.
While there are no hard numbers for the sales of PS4 Pros, we do have hard numbers on the sales of PS4s on the whole. Almost 60 million units have been "sold-through" ("sold through" retailers, to consumers) since the PS4's launch in November 2013. Not only that, Layden alleges that the PS4 outsells the Xbox One by 2-to-1 in North America and 3-to-1 in Europe. The presumption is that these sales do not reflect lifetime sales, since we last heard in January that the Xbox One had hit 26 million in unit sales. Without real context to those remarks, it's hard to gauge the true significance of those numbers, but it can be assumed that the PS4 is currently outstripping the Xbox One in raw sales.
Layden highlighted other pluses for PlayStation as a whole - the PSVR system has exceeded a million units sold, without a day having gone by where it hasn't been sold out.
And while the sales for the PS4 Pro are clearly going well for Sony, Layden went to great lengths to reassure owners of the base PS4 that game development is still "slaved" to the capabilities of the earlier machine - meaning that we won't be seeing any games purely for the PS4 Pro anytime soon. However, Layden refused to guarantee that this approach wouldn't change in the future, saying only that for today, they were "going to stay the course".
Sony apparently does not consider the Nintendo Switch a competitor to the PS4, stating that he saw the two consoles as two separate parts of the same ecosystem - echoing previous sentiments towards the PC market.
"When you look at our numbers, I think it shows that a lot of gamers are a two-console family. [...] And quite often those two consoles are PlayStation and Nintendo sitting side-by-side."
Finally, Layden touched briefly on the idea of a PS4 version of the Xbox's Elite controller, saying that it was something they had looked at doing, and would continue to look at.