Adobe will officially announce the 4th version of the Creative Suite on September 23, 2008. Be sure to sign up for the webcast of the announcement.
At the TODCon conference I attended in June, Alan Musselman highlighted the new features in Fireworks CS4, and they looked great! I know a lot of web professionals who have downloaded the CS4 beta versions from Adobe Labs, and have been very impressed.
Note: September 23, 2008 is the announcement, NOT the official release date of Creative Suite 4.