Analyst Gene Munster (via Appleinsider) published a report on his expectations for WWDC.
Munster expects new MacBook Pros and "also possible" a new iMac at the developer's conference in June. This echos many recent rumors reports found on the interent. As well, he expects that Apple will host a separate event in late June to launch the iPhone, rather than launch at WWDC itself.
Meanwhile, it appears Munster uses our Buyer's Guide as a source of information on updates:
He notes that on average, the Cupertino-based company has updated its professional notebooks every 182 days, with the most recent generation having launched 209 days ago. Similarly, he said, iMacs have traditionally seen updates every 168 days but the current generation is now a whopping 257 days old.
This data correlates to our Buyer's Guide numbers which are generated based on our own product tracking statistics.