Is this upgrade switcheroo procedure possible?

I'm currently using an iPhone 4, contract free.

My friends iPhone 4S contract ends in May 2013.

The plan is for me to purchase the iPhone 5 at the fully subsidized price, and for him to end up with that phone and the new two year contract, and for me to end up with his 4S and the contract ending in May 2013.

If this is possible, I figure it works out well for me because I get a 4S now for free, I can sell my 32GB 4 for at least $200, and then I'm contract free again when the 5S comes out and can upgrade to that.

 

Well, if we did this, he would be buying me the 5S next year in a similar procedure.. so we'd just be trading back and forth between who has the newer phone... but if I don't do anything I simply remain contract free and purchase the 5S next year anyway...

I'd prefer he just wait until next year and we both get the iPhone 5S.. that seems to make the most sense.