you should be able to find a 1020 for a pretty reasonable price off contract if you want to save a subsidized upgrade for something newer.
i currently have a 1020 and had a 5s and a 1520 and my sister has an icon. the 1020 still takes some of the best pictures i've ever taken with any phone i've ever used.
the screen looks like a step back when you go back and forth between the gorgeous (but way to large imo) screen of the 1520 and the amazingly sharp screen of the icon. but after you readgust to it, it's still a great screen. i miss my third row of icons.
personally at this point, with build looming ever closer, i wouldn't sign a contract for the (now) antiquated 1020, but i would probably pick one up off contract on CL or the like for the $300 or so they're going for. if you don't want your iphone anymore, you could probably make a trade or a buy/sell and net some cash in your pocket.
so the tl;dr version:
screen is a step back but still great
you won't notice the processor improvement in the sd800 (for now)
camera is still the best out there