Apple has a mind of their own and they forced at&t and VZW's hands in the first place regarding the iPhone. When the iPhone first came to at&t, Apple made all the rules and at&t couldn't say anything. So there is a 50/50 chance that the next iPhone supports 800SMR CDMA voice. It'll be a miracle that Apple allows 1900 LTE on it.
Side note, If anyone has an iPhone 3GS they aren't using anymore, please PM me. Mine died early this morning on me.