Dell is currently selling laptops with Core i7 already so that alone puts a little pressure on Apple. Not that fanboys wouldn't purchase new MBP's with a 486 inside.
While the macrumors buyers guide is generally a good place to go to get a vague sense of the upgrade cycle--it is partially based on the timing of the Macworld convention that Apple no longer participates in.
I have a feeling this year that we *may* see updated MBP's just in time for the Christmas buying season--but I base that upon nothing but speculation.
If not in the next month or so, then the beginning of 2010 for sure.