I doubt we'll be seeing that much better performance, since most devs are not going to want to spend a ton of time optimizing for the new hardware to truly take advantage.
The capability is there on paper, but as you said it all comes down to how developers use it. Personally, I don't see there being much in the way of resources, time, and financial incentive to optimize for two PS4 formats, even if they're somewhat similar. This goes double considering they won't see a considerable bump in their sales to justify the extra resources required on their part.
Taking FF15 as an example, Square Enix is already spending a ton of time and effort trying to get their engine to run decently on current-gen hardware. They're gonna keep optimizing up until the very end, and even still I don't foresee a rock solid 30 FPS out of the game. To add a Neo performance profile on TOP of everything that they're doing? I'm willing to be a lot of devs will not focus on it at all, since they're required to ship on regular PS4 as well. Post-launch performance patches I can see being a thing for devs under a time crunch (aka most of them), but still, do people really want to buy another console to wait longer post-launch to get a customized performance profile for marginally better performance? I guess if people have money to burn or they're completely new PS4 adopters in which case the profile will be just gravy, but otherwise I don't think it'll be worth it at the end of the day.