Still wary of server overload, Apple may keep the iPad version of Siri exclusive to the new third-generation iPad. As recent reports have shown, the iPad 2 still has much larger market share than the new iPad, and keeping Siri out of the hands of iPad 2 users will a) reduce server load, b) encourage users to buy new iPads.
Of note: Siri's window won't be full screen on the iPad, which makes sense. It would be wasteful, and perhaps even strange-looking, for the entire 9.7-inch display to be covered by Siri's user interface. Instead, 9to5Mac revealed a mock-up that reminds us of nothing less than the 2X mode app user interface from when the first iPad debuted.
Those who remember that time will recall that apps that were not iPad-optimized would appear as a small iPhone-like window in the center of the screen. Users could click a button to zoom the window larger, but it was still a clunky UI.
While Android tablets still suffer a dearth of tablet-optimized apps, apps run on Android tablets without optimization or recoding, without suffering this sort of malformed display. However, what does appear on some Android apps without tablet optimization is a rather wastefully displayed interface, with a lot of blank areas on the screen.
iOS 6 is expected to be introduced at Apple's WorldWide Developer Conference (WWDC) in San Francisco, running from June 11-15. We expect that although the OS will be introduced then, it won't be released until the iPhone 5 debuts in the fall. That belief is confirmed by Apple itself, in that developers have not even had a preview version delivered to them yet.