re: AT&T will cut its Next payment plans from 4 to 2 starting on June 9

This is actually an improvement over the previous next plans. You could always get a new phone every year with the next plan, but you were paying 60% of the phone's value (+ all sales tax) instead of 50% before trading it in. They've made it more enticing to upgrade yearly, probably due to pressure from smartphone companies.

The 24-month payment plan hasn't changed. As before, you're paying 80% of the phone's value (+ tax) and then giving it back. You'd be better off financing it under the new-phone-every-year plan, paying it off in 24 months, and selling it.