In the second calendar quarter, Apple sold 2.6 million Macs, 4 percent more than the same quarter the year before . Only 849,000, or 34 percent of that total, however, were desktops, which the iMac dominates. That was down 10 percent from the 943,000 desktops sold in the same period of 2008.
Gottheil also hedged his bet. "The iMac is the longest in the same box," he said, referring to its case design while and acknowledging anything's possible from the Cupertino, Calif.-based computer maker. "Apple is completely unpredictable."
Another hint that Apple may do the unpredictable comes from history's timeline: Last year, Apple unveiled the new "unibody" design for the MacBook Pro in mid-October.
Also worth noting is the MacRumors Buyer's Guide , which tracks the product cycles of Apple's hardware, and makes recommendations based on the average time between refreshes. According to the guide, the iMac has been updated every 220 days, on average, since it's 2003 introduction. As of Thursday, 203 days had passed since the March 2009 revamp.
"Buy only if you need it -- approaching the end of a cycle," the buyer's guide warns.