LOS ANGELES (Reuters) – Walt Disney Co agreed to buy filmmaker George Lucas’s Lucasfilm Ltd and its “Star Wars” franchise for $4.05 billion in cash and stock, a b lockbuster deal that includes the surprise promise of a new film in the series in 2015. Disney Chief Executive Bob Iger told analysts on Tuesday that the plan is to release a new movie in the series every two to three years thereafter. The last “Star Wars” picture was “Revenge of the Sith” in 2005, and Lucas has in the past denied any plans for more. …