Can I get upgraded to an iPhone 5? AT&T?

I got my phone last December, (iPhone 4s) and my contract ends in September I think. I've gotten some text messages saying I'm eligible to come in and trade my phone in for an iPhone 5, but I never asked my dad if I could. My birthday is coming up.
So anyway, here are my questions:
1. Can I get upgraded?
2. Has anyone else upgraded after about 10 months?
3. Would it be expensive?

AT&T's contracts are 2 years, so you can't upgrade… Well, that's not true, you can upgrade but you will have to pay the full retail price of the phone that you want.