As noted by MacStories, Apple has seeded the golden master version of Xcode 4 to both iOS and Mac OS X developers. The "golden master" designation indicates that this version of the software is intended to be the final version released to the public, barring any last-minute issues.
Xcode 4, which first debuted for developers at WWDC last June, offers a significant update to Apple's development environment for Mac OS X and iOS applications. Most visibly, Xcode 4 features a new single-window interface, but a number of other enhancements are also included.
A public release date for Xcode 4 remains unknown. Major Xcode releases have, however, traditionally accompanied Mac OS X software releases. Xcode 3.0 was released alongside Mac OS X Leopard in October 2007, while the Mac OS X Snow Leopard release in August 2009 saw the release of the tweaked Xcode 3.2 that serves as the current basis for the development environment.
MacStories notes that the release notes for Xcode 4 list Mac OS X Lion as a requirement, although this is almost certainly an error given that no Lion seeds have been made available to developers and the description on the download page indicates that Mac OS X Snow Leopard is required. Mac OS X Lion has been pegged for a release sometime this summer.
Update: The golden master build of Xcode 4 appears to have been pulled from Apple's site, with only the earlier Developer Preview 6 currently available for download.
Update 2: The golden master build is available once again and no longer makes reference to requiring Mac OS X Lion.
