I hear that all the handsets are going to a common standard. Sprint/Nextel units will essentially be on a 3rd standard that is basically VOIP. Don’t know the details beyond that. NEXTEL may survive as a brand, but it doesn’t look likely.
spint/nextel and verizon are the old US system which while higher speed is only used in the USA. Everywhere else is pretty much GSM which is the euro based system.
Of course OUTSIDE the usa, the simple switch of a simm card and you can change phones like a necktie.