That would definitely work out. I don't consider that an extreme measure either, because you're saving some money with very little work.
However these are some factors you may want to look into...
If you get the right Rep, you will be able to do an early upgrade. As a matter of fact, just call customer service and see if they can notate your account to give you an early upgrade. The store has to honor it.
If you want to be sneaky, if you have any other att phone, momentarily put it on and take the blackberry feature off. Then call in customer service and tell them you want to upgrade to a blackberry. Tell them they should give you an upgrade since you will be increasing revenue for ATT...it might work.
An early upgrade can definitely be possible if you know what you are doing.
If you want to cancel and do the new activation, check how much the ETF is. They are pro-rated now so they could be less. If you want to keep your number, just port it to Verizon, then port back to ATT.
There is an exceptional 1 year upgrade where you get 75.00 off the retail price...up to you though.
I say go for the 2-year upgrade...if you try hard enough you can get it.