Carnival Luminosa opens its first San Francisco homeport season from Pier 27, sailing four-night Baja getaways and 10-night Alaska itineraries — and exposing the limits of loyalty perks when a sailing packs in so many Platinum guests that priority benefits get suspended. And Cunard unveils a Queen Mary 2 voyage built around America's 250th anniversary: a seven-night July 4th sailing from New York to Newport and Halifax timed to 'Sail4th,' the largest tall-ship flotilla ever assembled.