Hmm - everyone is assuming the 5 will still be available at a reduced price once the 5S/6 is released, just like every other year, but that's not counting on the supposed "5C" or budget iphone seemingly coming this year.
Apple keep a very, very right rein on inventory. If they're launching a budget iPhone to take the traditional place of "last year's model" in the lineup, then it's quite possible that we'll see the iPhone 5 pretty much disappear at the same time. Certainly whatever stock is out there may simply remain at the same price, with the 5C undercutting it and the 6 at a premium. It doesn't make sense that they'd launch a cheaper, new iPhone with a big fanfare while at the same time making the better built and more premium iPhone 5 cheap too.
So if you don't fancy the cheaper, plastic, budget model, and the price of the 5 is right for you now, maybe it's not such a bad idea..