Necrobutcher was interviewed on Total Rock Radio and he made it clear that they are actually working on new material but that it may take a while until it comes out, as the members of Mayhem have side projects, so they keep being busy and it's hard to get the right inspiration.
Still, sounds like they are having a blast at the moment, and all we can do is wait and see!
Sadly, Mayhem's website is under construction, but you can always read more about them here:
http://www.myspace.com/officialmayhem
