The iWork updates appear to be fairly sporadic. iWork '09, the current version, was released in January '09.
Many people expected iWork '11 to debut with the Mac App Store in January this year, and and every event subsequent to that. An update could be imminent, it could be months off, it could never happen.
You could always try Apple's 30 day free trail of iWork to tide yourself over for another month, but if you need it now, buy it now. And also bear in mind that it's not like a hardware update, where if you buy at the wrong time, you're out thousands of dollars; it's a relatively cheap software product.