In the excellent and totally free web magazine Mass Movement #35, there is a Pat Mills interview, and the man talks among other thing of the Sláine "30th anniversary story : Book of Scars in August. 6 stories x 6 pages each: Clint, Glenn, Mike McMahon and Simon Bisley. Followed by a new Sláine by Simon Davis."
It is already possible to pre-order the harback that will follow the August pre-publishing in 2000 AD (scheduled for November). Try here (for example only).