If the design is the same, no, I will not upgrade. I love how the iPhone 4 looks, but I don't like the iPhone 4 itself. One example, I like my phone naked, but the plastic on the edge hurts my ear when I'm talking on the phone for longer than a minute. Just a little quirk. There are a few others.
If the design changes, I will most likely upgrade, but keep my iPhone 4, for aesthetic value. I really do think it's beautiful. No design change I'll probably spring for a Blackberry Bold 9930. I have two upgrades available, so it's not like I'll have an upgrade available for iPhone 6. And I'll be keeping the iPhone 4 to switch back to whenever I please...