It's completely your choice, but don't you use your computer for more than gaming? A computer can do more than gaming, whereas a console such as the PS4 won't be able to. If you're not able to upgrade your existing computer, then it maybe safe to assume you're short on cash?; if so, sticking with a PC which can also do more than gaming seems the most appropriate course of action.
If you're satisfied with your system, I'd stick with it to be honest. Going to a PS4 may leave you with regrets. Then again you know what they say, "no pain no gain" regardless I don't think that phrase applies here. There's no guarantee gain with a PS4.
Personally I use my computer for developing for the web, iOS (via VMWare), Android alongside using software such as Adobe Photoshop and even the minor Microsoft Office (amongst many more software). I also do use my computer for gaming casually, nothing serious (I'm not fond of many games, only GTA, Far Cry 3 and Watch Dogs). With all that said, for me I'd stick with a computer (and I don't have a console). Of course you'll use your computer for different purposes, so it's completely your call.
All in all, it's your choice.
All the best.