Daniel Phillips, a lead Tux3 developer, wrote to the kernel mailing list on Monday and acknowledged that it's been a long time coming for Tux3... We covered Tux3 back in 2008 as the Tux2 successor that was never merged due to licensing issues and then it had been quite some time without any news on Tux3, until it was resurrected in early 2013.
Since then Tux3 has gained fsck support, wild performance claims, and as of a few months ago was planning for future improvements.
In his latest mailing list post, Daniel Phillips describes his latest blocker items for merging Tux3 as being an allocation policy, mmap consistency, and ENOSPC support for the file-system. With those three main items left to be achieved for Tux3, the file-system would be in better shape for review and ultimately hitting the official Linux kernel. Interestingly, those items are close to being achieved so we may see Tux3 up for review in the months ahead and it being merged in not too many kernels from now.
For those interested in the Tux3 Linux file-system, more information can be gathered from the lengthy mailing list post.