Next year’s Milan Expo isn’t until May, but with a theme of food it’s no wonder 6 million tickets are already sold. The Expo is the modern incarnation of the old World’s Fairs that thrilled 19th and 20thcentury audiences with new products and futuristic technology. While the Expos have lost their gee-whiz luster, 20 million people are expected. Milan’s famous opera house, La Scala, is normally closed in the summer, but will host concerts and performances daily during the Expo. Tickets are $45 a day, but organizers say most visitors will need two or three days to see the massive event, which will feature exhibits, marketplaces and entertainment including Cirque du Soleil shows.