Unless you need LTE, you should really consider buying an iPhone 4. The small increase in screen size for the new phone isn't worth the hundreds extra you'll pay for it. The iPhone 4 has the same chip as the first gen iPad with more RAM, so it will be well supported for at least another year. You'll also get the same high dpi Retina display.
If you wanted to, you could spend more for a 4s and you'd get an A5 dual core chip....probably guarantees you two more years of support.
This is what's so disappointing for many of us. As much as I wanted to, Apple gave me ZERO reason to upgrade last year, and this year it looks to be LTE (not sure about coverage for me, or extra data cost). The new iPhone itself is not as attractive as the 4 or 4S and the additional half inch screen length just doesn't seem worth it.