Okay, so we might or might not be getting an official app from Google anytime soon, but the day is not a complete waste as they finally enabled (fixed?) their mobile version of the site.
Up until recently, if you navigated to plus.google.com in IE on Windows Phone NoDo (or earlier), you would have been greeted with a message saying your browser was incompatible, which is pretty lame. On top of that, Google's site still only lists Windows Mobile for mobile site access (c'mon, guys, show some respect!). Now at least, you can use Google Plus via Mobile Internet Explorer with ease.
While not a full dedicated app, at least this gives you basic access. Of course, the point is a bit moot if you run "Mango" as IE9 acts like a desktop browser--so that was always working with the site. (Thanks, loof, for the heads up!)