AT&T Inc. executives are working on a blueprint internally for a potential acquisition of Europe's largest mobile carrier, Vodafone Group Plc, sometime next year. At the present moment the companies haven't entered in any formal negotiations because a deal can't happen until Vodafone's sale of it Verizon Wireless stake is done, that is expected to happen in early 2014. The merger would create the world's largest telecommunications company by sales. If the two companies combined the company would have a market cap of $250 billion with operations throughout the U.S. and Europe, with of 500 million wireless subscribers.