This is exciting. The promoters of Sonisphere UK 2011 have just confirmed that the Big 4 will be headlining the first night of the 3-day event happening between July 8th and 10th. This will be the first time all four legendary bands will share the stage in the UK. The bands played a few Sonisphere shows in other parts of Europe this past summer, one of which was taped in it's entirety and featured all four bands getting on stage to jam to "Am I Evil?". I think this should be considered a good sign that the Big Four may finally be coming to America, as Mustaine seemingly hinted at. If the bands are already in touring mode, there is no reason they can't hop back over the Atlantic for what I predict will be a stadium tour. More info about tickets and travel to the fest could be found here.
