As a follow up to yesterday's article, here is a tidbit from 9to5mac on Best Buy. Looks like they are getting back the iPhone 4 and 4S trade-in for $150 credit towards iPhone 5, that itself has $50 slashed from its original price of $200. So essentially you get a new iPhone 5 for free if you have an older iPhone 4 or 4S.
However note that all these promotions are because Apple is expected to release a new iPhone in the fall of this year. So if you buy a new iPhone 5 now, it will soon be a year old model. Also trading in an iPhone 4 is more profitable than iPhone 4S with this deal.
Also just noted that you can actually get more than $150 for your trade-in and can get a Best Buy gift card, ok then trading in your iPhone 4 or 4S should not make a difference.