I've just purchased a 4S on contract in the UK for £30 a month with unlimited data & tethering and no up front cost for the handset.
I figured that I'm not too bothered about owning the 5 (the very small screen size increase isn't enough to lure me, and the 4S camera & Siri were enough for me), and the 4S is unlikely to get any cheaper when the new phone is introduced (the iPhone 4 is only a couple of pounds cheaper per month but without unlimited data).
If you're not bothered about the latest and greatest, and you live in the UK, now's a great time to buy a 4S.