Well Winter NAMM 2012 is over, and we still have very little information about the Marshall Satriani Signature amp.
Chris George from Marshall hinted that it would be released in a few months on Twitter and also in the 2nd video below he mentions that more gear will be released at Musicmesse in March. Satch himself (When interviewed by The Tone King) only commented on the existence of a prototype and a few of the changes from the stock JVM410H, with no specific info about the release date. Check the videos further down this blog post.
Perhaps we will see the Satch amp released at Musikmesse at the end of March then, and I also assume some more gear will be released at Summer NAMM in July