The 20 year old actor Nicholas Hoult (Clash of the Titans, Skins) was on GMTV this morning, talking about a recent trip to the slums of Nairobi, on behalf of Christian Aid. During the interview, his role as Nux in Mad Max 4 was mentioned. Sadly, apart from confirming that Chalize Theron is in it, he had no more to say. Presumably, it's all still Top Secret.
So this isn't news as such, but does confirm that pre-production is in full swing and that principal photography is due soon.