The current camera on the iPhone 4 is stellar IMO and many others... an equal 8MP camera would be even better....
Not necessarily. If the photosites on the sensor are still the same size you will get a worse picture. Higher megapixels != higher quality picture. In most cases they can make pictures worse by adding noise.
Maybe an 8mp bump will work in the iPhone, maybe not. Depends how the image sensor is created and how the lens is. Unfortunately Sony doesn't have the best track record with consumer imaging. I'd be more excited if Canon was making the camera.