Trying to keep my Unlimited Data- I want help verifying my plan to do it-

[AC Question]

Here is my situation-

My Line, Line 1- UDP, Galaxy S4, Upgrade Available
Wife- Line 2 UDP, iPhone 4s, Upgrade Available
Line 3- Dumbphone , Upgrade Available

Here is what I want to do-

I want to upgrade my wife to the S5, and when the Note 4 comes out (I know there is a risk that Verizon will close this loophole before I get my chance), I want to upgrade my line to that one.

What is the best method to do this, without paying full price?

Thanks for your help