I'm not asking for peoples opinions or what they think about the next gen phone, I am asking for anyone pursuing this route now or soon. I've never gone this path before but I recall in years past how phone values drop a lot when the new one is announced and want to try a new plan this yr to avoid signing a new contract all the time (however I am on a fam plan and we all rotate upgrades but I dont' see a need to if I can upgrade my phone by selling and buying outright for the same price as upgrading).
The latest rumor puts the iP5 release around September I believe. You seem to only be focusing on the resale value of your iPhone 5, and not the resale value of the phone you'd be using in between -- such as the HTC One you mentioned. The resale value on that phone will be lower as well since they are readily available and by then there will other more advanced Android handsets. Hype is already building for the rumored Motorola X that is apparently going to be high end, available on every carrier and run pure Android.
I think it would be a lot less trouble and probably no more expensive to simply wait for the iP5 and sell your current iPhone then--even at the discount.