While trying to figure out why my TUAW Tips mailbox just choked and cried uncle, I finally found the source of the clog: too many tips to count started pouring in that the announced September 12th special event (not to be confused with the 25th) could be the announcement of a 23-inch iMac Core 2 Duo, not to be confused with the Core Duos in many Macs right now. This new chip is code named Merom (aren't Intel and their code name games cute?) and promises a 40% performance increase over current Core Duo chips, but with zero increase in power consumption.
This rumor has blown up everywhere, from AppleInsider to MacRumors and, of course, Engadget. September 12th could easily be something big, as it isn't simply some arbitrarily chosen day - it coincides with the first day of Apple Expo Paris.
Speculators - start your engines.
AppleiMac 27-inch with Retina 5K display (late 2014)