We think we have come up with a solution for this. We are doing two things, one for the keyboard and the other for the UITextView.
For the keyboard we are setting the status bar orientation. The keyboard follows when set.
[UIApplication sharedApplication].statusBarOrientation = UIInterfaceOrientationLandscapeRight;
And to get the UITextView to orient correctly we apply a transform to subviews of our EAGLView, which in this case is only the UITextView, as follows.
CGAffineTransform aTransform = CGAffineTransformMakeRotation(M_PI / 2);
[glView UpdateSubViewTransforms:aTransform];
This literally adds a 90 degree rotation to the view.
This has been tested on iPad & iPhone 4 with iOS 4.3, and on iPhone 3G with iOS 3.13.