Details are coming out today about the new CS5.5 update. Adobe's site is loaded up with info which I've aggregated below. They are saying we'll see a release of this update in early May and you can pre-order your upgrade right now.
One of the most interesting new details about this release is that Adobe is going to start offering a subscription service that allows you a number of options to pay an affordable monthly price for use of either individual applications or a whole suite. See this video for details: http://tv.adobe.com/watch/cs-55-design-premium-feature-tour-/cs-subscription-overview/
List of CS5.5 related videos and articles on adobe.com: