The Ubuntu Desktop Next 15.10 Daily Builds with Unity 8 are now available for download, being the first system to receive the new Ubuntu Wily features.
As expected, Ubuntu Desktop Next 15.10 runs over Unity 8 and Mir, but the stable version of this OS will still use Unity 7 and X.org, as default.
The Live Image ISO images are available for both 32 bit and 64 bit architectures and can be downloaded from the Ubuntu website.
For now, much information about the upcoming features of Ubuntu 15.10 is not available, but one thing is sure, it will be using either Kernel 4.0 or Kernel 4.1 as default (Kernel 4.0,4 has been already implemented).
Because it is in its early development stages, Ubuntu Desktop Next 15.10 it does not bring too many changes to Ubuntu Desktop Next 15.04, but however, if you want to test it, I recommend you do this in a virtual environment.