As Matt Cutts noted in his comments on Sphinn – about 88 days back – we can safely assume that the next Page Rank update should be round the corner and should fall around new year. (or as soon as Googlians return from their vacations?) This is what he has to say-
I’m glad that new PageRanks showed up this weekend as expected; after this toolbar update, I expect us to get back to the normal 3-4 month cycle.
So, be prepared. All the Best!
Ankur Jain is a Software Engineer in Test Automation. After a 5 years stint with Accenture and Oracle, he started his eLearning company. A long-time blogger and proud owner of the "Learn" series of websites. 
Thanks vlad. Fixed that now. 🙂
The link to mattcutts.com is broken. You forgot http:// 😛