It's, officially, a one way transition - you can CT/Port old-gen accounts to PC, and NG accounts, but not the other way. But that said, it's pretty clearly stated in R*'s info about CTing.
Maybe, eventually, there may be a way to chance the flags in a PC account to allow a reverse move to NG console - but since i strongly suspect it would have be server-side action to instigate (and remember, manipulating a server to force it to rewrite data/make changes unauthorised is a criminal offense in a lot of western nations) and it would be almost certainly a LAN or virtual LAN side function, not accessible from the WAN side.
If you know anyone with a PS3, jailbroken or using mods under OFW, who's got GTA V - you'll be better off getting them to create a new hacked/modded acount on PSN to CT to PS4.