Walt Disney Co. on Wednesday agreed to buy filmmaker George Lucas' Lucasfilm Ltd and its Star Wars franchise for $4.1 billion in cash-and-stock in a blockbuster deal that includes the surprise promise of a new film in the series in 2015.

The deal unites a boutique Northern California film studio that brought special effects into the digital era with a venerable Hollywood powerhouse that has shown a knack for getting the most out of entertainment brands.

Disney plans to release at least three more films in the Star Wars science fiction saga that ranks among the biggest movie franchises of all time, said Bob Iger, chief executive. The last Star Wars picture was Revenge of the Sith in 2005.

"It's now time for me to pass Star Wars on to a new generation of filmmakers," said Lucas. He will become the second-largest individual holder of Disney shares with a 2.2% stake.

"This is one of the greatest entertainment properties of all time," said Iger.