Apple has released Xcode 4 Gold Master Seed to developers signaling its public release is near.
What's New in Xcode 4 • Xcode 4 has a brand new, single window interface for all major workflows • Interface Builder is now integrated within the main Xcode IDE • Assistant shows a paired editor with complementary files (headers, UI controllers, etc.) • Fix-it highlights code where an error is detected, as you type, and can even fix it for you • Version editor shows a live comparison through SCM history, using Git or Subversion • LLVM compiler 2.0 includes full support for C, Objective-C, and now C++ • LLDB debugger is faster, and uses less memory than the GDB debugging engine • Instruments adds System Trace, and new iOS instruments including OpenGL ES
Developers can download Xcode 4 GM Seed from the iOS Developer Center.