Do you know about MinGW-W64 project(http://www.sourceforge.net/projects/mingw-w64)?
This project provides 32-bit/64-bit runtime library and also native/cross 32-bit/64-bit compiler.
Though it's not very urgent to port Codeblocks itself to 64-bit. But users may need to use Codeblocks to build 64-bit application. So I think, in the comming release, we could provide both MinGW and MinGW-W64 compiler.
I have successfully built the compiler from GCC 4.4.3/GCC 4.5.0 and MinGW-W64-CRT source(both 32-bit and 64bit), and also wxWidgets.
1. 32-bit/64-bit support
2. Fully UNICODE support. that is with --municode link flag, the entry point will be wmain/wWinMain other than main/WinMain, just like MSVC.
3. TLS(Thread local storage) support. MinGW's runtime doesn't support this.
Throw this project is currently in beta now, but it's already very stable now. Downloadable binary is in its project page, the Win32/Win64 personal-build by sezero is recommanded.