From the MacRumors Buyer's Guide
Macbook Pro
Days since last update: 192
Average days for update: 267
You can hardly consider the MBP refresh as "late". Technically, based on averages the next MBP shouldn't be released for another 75 days, putting it somewhere around mid July. If August hits and we don't have a refresh, then you can start crying foul. But I expect the refresh in June.
But that was hardly an "update". That was the smallest change Apple's put into the line in quite a while, if I'm not mistaken. Tiny bumps in processor speed and HD cap. No notice online, no fanfare from Apple, store was just down for a few hours and the product changed.
But perhaps it seemed tiny because of all of the "air" rumors. I've been waiting since *before* that "update" for to get a replacement for my MBP. I really like the idea of a 15 or 17 "air" style machine....