Update: Backtracking, Microsoft has now disclosed that there will at least be a single public beta, stating that yesterday's assertions left the wrong impression. While there is still no confirmed date for the open beta, if it follows Office 2007's path, a download could be available in November.
Microsoft confirmed today that there is currently no plan to open a public beta phase for Office 2010. They will instead offer the preview to a predetermined group of several thousand users in the third quarter of this year. This approach is somewhat different than previously used during the development of Office 2007, which had a couple open beta periods in 2006 and in-between, users could experience the new office suite from within their browsers.
Previously carrying the codename "Office 14", Microsoft Office 2010 is expected to be available in both 32 and 64-bit varieties and will include IE, Firefox and Safari compatible browser-based versions of its core applications. As the moniker implies, Microsoft is aiming to release Office 2010 in the first half of next year, which will follow the highly anticipated Windows 7 release.
For now, though, you can at least get a taste for the coming Exchange 2010.