At this point, I feel like the people that will be swayed by the "most powerful" argument have already bought a console. If you stayed on PS3/360 for three years into a new generation, your primary concerns are mostly gonna be software library, affordability, and where your friends play. If you cared that much about power, you would have already bought the basic versions of XB1 or PS4. The reason for budget gamers to upgrade at this point is that their favorite franchises are no longer appearing on last generation consoles in proper form, and most people on their Friends list are playing on a different platform.
This will be a hurdle for the Scorpio as well, though.
I feel the 399 price is an attractive one. People buys tons of tech toys these days. Xbox sales got a boost with the S model. The 4pro will give a more tangible improvement. No Blu-ray 4k disc, no problem for most of us.
4pro is just expanding the mid-gen refresh, not much difference from previous PlayStation, one more option is better for all, besides for the developers i guess.
Sony has clearly communicated this to us, publishers and developers, their plan is laid bare. They are also open to iterative no-gen consoles, but right now the 4pro is handled the same as the past.
Scorpio on the other, we are not sure about where MS is heading with their consoles, UWP and all, coming off the disaster of Xbox 1 and their w8/10 mobile push.