Rather than wait for Facebook’s big announcement on Tuesday, Web watchers are trying to predict what the social giant will unveil. TechCrunch’s Alexis Tsotsis is putting her money on Messenger for the iPad. “While my colleagues are hearing that this ‘what [they're] building’ is a ‘big deal’ -- as in a ‘phone’ or a slew of ads and other improvements -- I’m hearing that one of the products that could be announced is Messenger for iPad.”