UPDATE: Well that was fast. There is already a rumour suggesting something different. iMore claims that the next-gen iPhone 5 have the same 3.5-inch screen and won't launch until the fall.
It only took a week after the New iPad launched for the iPhone 5 rumours to start. This one comes from media in South Korea, who reported that the next-gen iPhone will have a 4.6-inch retina screen.
A rumour saying that the iPhone 5 will have a larger screen is far from out of this world; many expected it from what became the iPhone 4S. But 4.6 inches is almost as big as the Galaxy Note, which is as much a small tablet as it is a smartphone. So take the exact sizing with a big, fat grain of salt.
The report also suggested the iPhone will come out during the second quarter, which suggests that it would be announced ahead of the Apple Worldwide Developers Conference. That again seems unlikely, but hey, who knows.
Now that the first rumour has surfaced, it will only be a matter of days before a counter-rumour pops up. And, like always, some rumours will turn out correct, and some will turn out horribly wrong.