Looking through the top charts on the app store (most of which are games), it seems that most apps were not made in objective-C. In order to keep up with the competition, is knowledge of objective-C still sufficient for iPhone development? What other frameworks should be considered necessary?
Yup. It's currently the 6th most popular language: <a href="http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html" rel="nofollow">http://www.tiobe.com/index.php/content/paperinfo/tpci/index....</a> (among all of IT, not just iOS)