Comcast announced late Wednesday that it will launch faster broadband Internet service speeds over the next few weeks to more than 10 million homes and businesses. The new service will give Comcast subscribers access to speeds of up to 50 megabits per second in parts of New England, Boston, Philadelphia, Minneapolis and St. Paul, and New Jersey. The upgrade will also enable Comcast to double the broadband speeds of its entire customer base at no extra charge to subscribers.