The final Linux 2.6.38 kernel should be released in the near future with its Radeon HD 6000 series open-source support, AMD Fusion Linux support, ATI page-flipping, Nouveau Fermi acceleration, and many other open-source graphics improvements. This kernel to be used by Ubuntu 11.04 also has EXT4/Btrfs changes, pulls in a kernel patch that does wonders, and offers other kernel improvements.
As said in the Linux 2.6.38-rc8 announcement:
I would have been ok with releasing this as the final 38, but I'm going to be partially unreachable for several days next week, so I felt there was no point in opening the merge window yet.
Also, we do have regressions. Some of them hopefully fixed here, but it won't hurt to give it another week.
So it looks like the Linux 2.6.38 kernel should be released early next week. After that, we can start getting excited for the Linux 2.6.39 kernel merge window as various new features are pushed.