We'd heard rumblings before, but if true, this warning is a pretty clear indication of a refresh. The current iMac line, released in late April 2008, probably isn't due for any kind of massive redesign. The most obvious reason is that it just isn't very old, especially compared to its nearly-senile relative, the Mac Mini. There also haven't been many rumors floating around about new iMacs, but it does look likely that the desktops will get a bump from dual- to quad-core procs in time for the release of Snow Leopard.
This is based on anonymous sources, of course, and without confirmation from Apple (which we won't get), this stays classified as a rumor. But it might be a reason to hold off on a new iMac purchase, at least for a little while. [AppleInsider]