The Street reported that Apple has picked a 8MP sensor from Sony for the upcoming 2011 iPhone:
"Apple has picked Sony's 8-megapixel camera chip for the 2011 iPhone, according to supply and manufacturing sources, said Rodman Renshaw analyst Ashok Kumar."
OmniVision reported that Apple ordered 5MP sensors from them for the next, 2010 iPhone.
2010: 5MP
2011: 8MP
Why posting iPhone rumors here? Because the iPhone is now the most popular camera on flickr.
Via MacRumors