IPhone 6 expected release date?

Ok, so I realise the 5s and 5c have only just been released, but if anyone knows when it's most likely the iPhone 6 will be out I'd be most grateful.
Currently on the iPhone 4, still works really well after 2 solid years of heavy use, updated to iOS7 turned off background app refresh and works a treat.
I can upgrade to 5s, but my network provider offer an alternative to reduce the monthly cost from 37 to £ 15 a month, on the same plan, unlimited internet, 2000 mins etc, which is a pretty good deal and it's only for 12 months too.
So, would it be wise to wait for the iPhone 6, if it's more than likely to be released in 12 months time?
Any answers grateful but would appreciate someone in the know and familiar with Apples sales patterns.

September 2014.

IPhone 6 will probably come out around this time next year.It'll probably have a larger screen with higher resolution, an even faster processor, improved camera, better battery, and 128 GB model.

But the 5S is great.

Sept 2014

Around this time next year. But you should get an iphone 5s.

I'm pretty sure it's around this time next year.