Well it is one of the puzzles associated with iphone 4, where apple stopped its white iphone after promising to release it along with the Black version. It is rumored that there were reception (more than the black) due to the white paint blocking the Radio signal and Deterioration of the paint due to heat.
But after the ipad 2 launch, everyone was confident that apple indeed will go back to launching the white version of its flagship product. But now one wonders whether there will be a major rejig of the back panel of the White iPhone? Will it be same as Black iPhone with a different white paint? or will be Aluminium as with ipad 2 ?. If no major change , it makes it more strange that Apple had taken this long to find the proper mix.