Trading in your current, or older, phone towards a much newer device isn’t anything new. Sprint has been doing it for quite some time. There are a few other instances of it out there as well. HTC is taking a similar approach and offering you a minimum of a $100 pre-paid visa gift card after you upgrade to a new HTC One. All you have to do is pre-register now with your email address, buy the One when it is available, then ship your old device into them with proof of the One purchase. They will turn around and ship you out a $100 gift card, or the current trade in value of your device ( which ever is greater).
Would you be willing to ship your current device to them for a little kicker card?