I never buy a console at launch. Well, I suppose I did acquire a ds not long after launch, and I didn't regret it, but consoles or handhelds are rarely worth acquiring right away IMHO. They may or may not have a solid launch lineup, but they need time to build up a library of games. Also, they are at their highest price point at launch. You don't need to be good at math to know that more games + a lower price point = better value. On the flip side though, if there are games you absolutely must have, then assess whether they will still be available later on. They almost always will though, unless you're interested in Japanese games outside of the mainstream titles that are either only available as physical copies, or you want a physical copy.
I do have a rule of thumb about having a list of at least 3 exclusives(or exclusive extended cuts) for the system that interest me, though I prefer to have at least 5. That way, even if said system doesn't do well, it still ends up being worth it to me, as a cult system. I'm not the type to go out and buy a system for one game, because between the cost of the system and the game, that's one expensive investment for just one game.
Depending on your age, you may or may not be awed by the graphics of the ps4's launch lineup, but it's up to you if you let that feeling guide you. Keep in mind there's only a small "whoa" period at the start of a gen, before those fancy graphics are accepted as the norm. What you're left with then, is the quality of the games. The ps4 should be a safe investment. Sony has never released a bad system IMHO, and their consoles have all fared well. With that said, there's nothing wrong with waiting and seeing how things play out, while saving a heap of money. Besides, not everyone is the type to camp outside overnight to acquire something they can get later on without having to wait, and deal with crowds; I'm certainly not. Even if you get a system shortly after launch though, despite possible shortages(another major con of going for a system at launch), there's still the matters of price and games. The decision is yours to make, but my opinion is that you should wait a little while.