I don't think that is relevant anymore. Most Macs are many months overdue since their historic average. Especially the mini and the iMac. Of course the WWDC is an good event to release MBP's, more so than consumer Macs. But I wouldn't really trust the historical averages anymore lately.
Though the age of the products might not be relevant I think the birth order still is.
Also, I agree that the iMac will not get LEDs yet.