WSJ, Apple is testing out various sizes for the iPhablet that range from 4.8-inches all the way up to 6-inches. We're not really sure that 4.8-inches should even be considered a phablet, even considering the largest iPhone available now is just 4-inches. It's possible that Apple has a different definition; but, the report also mentions that Apple is testing a 4.8-inch iPhone, so it could just be an oddity of the report itself.According to
The current set of phablets on the market range from 5.5-inches (Samsung Galaxy Note II) all the way up to 6.3-inches (Samsung Galaxy Mega). So, it's clear who Apple would be going after with this move. While there are other good phablets on the market, like the Huawei Ascend Mate, Samsung basically has the phablet market on lock with the Note.
There's no word on when Apple is planning to release said iPhablet, but it likely won't be any time soon if Apple is still in the testing phase.