Well, what games come out on the PS4 versus the PC is really going to influence if I get it. As of right now, I have no plans for purchasing one; and am fine gaming on my PC and 3DS. The only game I know I want that will probably come out on the PS4 is Kingdom Hearts 3, but I'm willing to wait for awhile for the prices to go down. So long as I have the console before the game comes out I don't really care. I don't feel a need to purchase it now.
I think that is what it ultimately comes down to for plenty of gamers: what games will be on it? If the games released are available for multiple systems, and you have a good PC, then you might as well do PC. However, purchasing a PS4 is cheaper than putting forth the money into a gaming computer, if you don't already have one. So then that comes into play. Some games would look awesome on a PC, sure, but not everyone can afford an awesome PC. There are people who just get the bare minimum for a computer and namely use it for work, school, etc.
I just recently got a good computer, so playing PC games was absolutely out of the question before then. My old one crashed when I played MapleStory. Binding of Isaac and Castle Crashers were the only games I really played on that one. Now I don't have any limitations. With this in mind, for myself, it truly comes down to the game. I'm a hardcore enough Kingdom Hearts fan that I'm willing to buy a console I may only ever use once just to play the new game.