There is no advantage to bumping the pixels. Users of camera phones are not printing billboards, they are mostly posting on facebook and instagram. Even printing your pictures on standard picture paper can be done with 8 megapixels.
As was mentioned I would rather have a larger sensor with larger pixels rather than more pixels. That will help in low light situations.
Apple is not a spec company. They only do what is necessary to improve function. Apple still uses a dual core CPU, one gig of ram and an 8 megapixles camera. if past practice is an indication, then Apple will stick with 8 pixels. IF Apple does it, it will be for marketing reasons.