This year, the best guess from Wall Street analysts, professional box-office watchers and Hollywood executives inside and outside the two studios is that “Harry Potter and Chamber of Secrets” (opening on Nov. 15) and “The Lord of the Rings: The Two Towers” (Dec. 18) will dominate the holiday season, taking in at least $600 million between them in the United States, and twice that much overseas. But many expect “Lord of the Rings” to beat “Harry Potter” this year.