Would you upgrade your iPhone, or wait for the new one?

I currently have an iPhone 5. I've been pretty happy with it, except my power/lock button has stopped functioning and my battery life is awful. I'm now eligible for an upgrade through my carrier, but the iPhone 6 is being released in September.I'm somewhat hesitant to upgrade because rumors say that the iPhone 6 will have a larger screen, which I'm not sure I want. However, I'm sure the larger display will become the standard and I'll have to upgrade to that size eventually anyway if plan to stick with the iPhone. What would you do in my situation, and why?

Added (1). I suppose I should clarify that I'm considering upgrading to the 5s now, rather than waiting to upgrade to the 6 in September.

One of the biggest mistakes ever is to buy a release date device. See, tech companies like Apple do not test enough their devices and they release them untested and full of issues (example of other companies that do the same thing: Microsoft with W8; Sony with PS4; MS with XBONE; Google with Nexus 5; Apple with Apple iOS7; and so on). If there are any issues, and there certainly will be lots, they release updates later throughout the year. I would not recommend you to get the latest iPhone yet. Wait a bit first for the first to buy it and start complaining, then get the second release that comes with updates and most of the hardware issues fixed.

Larger screens gives you more room. Smaller screens are not perfect if you want to depend completely on a smartphone for most of the computing requirements.

5S is a really good phone, it depends how long you are willing to wait for the next version.