That's entirely up to MKX/NRS, it has nothing to do with devkit vs retail. A profile is not required for the driver, it is required by the GAME for savedata and trophies and things. The PS3 driver itself doesn't care about any profiles or anything at all besides which sticks are plugged in. (Though I would assume you don't need to keep the controller actually physically plugged in, just not dead, so the 2 USB ports isn't really an issue unless you're at low battery, and you can probably plug the DS4 into another USB port like your phone charger, for power. That's some sideways spin there, heh.)
SG does NOT work that way, as already shown on repeated Salty streams. SG keeps the profile that started the game always logged in, and that's the only profile it uses no matter which controllers you add or remove. You need a single DS4 to press one button and dismiss the "You plugged in a legacy controller, the Home button won't work" message that you get when plugging in a PS3 stick the first time - and we're trying to fix that, too! - but after that point you can disconnect the DS4 and play the game entirely with PS3 sticks until you turn it off. I even wrote special code where if the DS4 was in charge of the menus, when you unplug it the game finds the first PS3 stick and puts that one in charge, which is not how other console versions work.
[edit] Just checked with my phone charger, you can leave a DS4 connected to your PS4 and charge it that way. If you connect it to something else that recognizes it as a controller (like your PC, with DS4 drivers) then it will disconnect from the PS4.
I don't have a GAF account, but there ya go.
