NO, your ACCOUNT will still have a 2 year agreement in effect. When you pick a NEXT device your ACCOUNT will automatically renew for 2 years, YOUR ACCOUNT not the phone line. When you purchase the next device and if you pay it off in a month your free to do with it as you please, BUT your account will still have a contract in effect for two years, so you would still have to be on a plan, meaning you will be charge a ETF if you close out your account.
If you buy a iphone 5s for $199 today and do a 2 year contract the contract applies to the account not the phone, your just getting special pricing because you signed a SERVICE CONTRACT on your account. When you upgrade to a next device your contract will reset to another 2 years, keep in mind this applies to the account, not the phone.
read the fine print, you will see this in there.
i actually went through this and thats how i found out.