The first beta version of the next major version of Freeciv, 2.4.0-beta1, was released in August 2012.
Relative to 2.3.x, new features include citizen nationality, saving map images for action replays, and easier authentication for servers -- in particular, the Windows executables ship with SQLite support, so for the first time it is possible to run an authenticated server with the prebuilt Windows server. For more information, see the summary of changes since 2.3.x.
Source code and Windows packages are available here.