Linux 4.0 [https://lkml.org/lkml/2015/4/12/178 has been released] on Sun, 12 Apr 2015.
This page is not complete. It will be completed in the next few days. Meanwhile, you can read about Linux 4.0 in other sites:
LWN: [http://lwn.net/Articles/632761/ The merge window opens], [http://lwn.net/Articles/633096/ merge window part 2], [http://lwn.net/Articles/634471/ The end of the 4.0 merge window]