I am an AT&T customer and I am currently eligible for a new 2-year agreement upgrade. My current phone is a Galaxy S4, but I want to have an iPhone again. (I'm done experimenting with Android). I definitely don't want to wait for the iPhone 6 to release before I switch back to iPhone. So, that means I'll be getting an iPhone 5s. (But I also want to get an iPhone 6 on launch day) Here are the options I came up with: 1. Use my current upgrade now to get 5s, and sell GS4 to cover cost of 5s.(And sell 5s to help get 6). 2. Sell GS4 and use that money to partially pay for an iPhone 5s at full retail, then use my upgrade on the iPhone 6 when it comes out tl;dr Should I use my upgrade on the 5s now, or on the iPhone 6 later? (I will be getting both phones) Which option should I go with? Thanks!