Tux3's Daniel Phillips has provided an update on the Linux kernel mailing list regarding the activity for this file-system. Due to other engagements, Daniel has had limited time to work on Tux3, but that is evidently now changing. Additionally, the atomic commit support is almost complete, which means that after some bug fixing and code cleaning, Tux3 may be on its way into the mainline kernel. In his mailing list message, Daniel regrets not trying to merge Tux3 into the mainline kernel tree back in February.
Daniel's full mailing list message can be read and followed in this thread. More on Tux3 is available from the project's web-site.