I think we're all in agreement about wanting to see an iPad app sooner than later. I'm simply theorizing about why we haven't seen it yet. You don't just stumble your way into an app that's as polished as version 2.0 without some kind of road map.
Let's say they started working on the current iteration of the iPhone app 6 months ago (or longer), I could see their approach as, "let's really nail the UI before we release the iPad app." Remember how so many people were waiting for an iOS Gmail app, and then it was released and had usability issues? And then the technorati pilloried them for the gaffe? Maybe that was a wake up call, and Google realizes that exceeding people's expectations is way more fun than underwhelming them.
Or maybe the timeline is as simple as: 1) unveil Google+ 2) give mobile users a basic app and find out what works well and how people use the service 3) develop additional apps based on findings from step 2.
That would make us beta testers, but I guess I'm ok with that