Comcast has been preparing its Xfinity Mobile announcement for the past two years, so it’s hardly a secret – and most US analysts in the run up to this announcement felt it would contain little or no threat to existing US MNOs. Our take on the detail is that this is a marketing tsunami set to take 8 to 10 million lines from incumbent MNOs in just a few years. The key element is pricing – no service fees for up to 5 phones per home – with unlimited free calls and texts– only data cost money and it comes in two flavors – unlimited at an existing Xfinity broadband customer at $45 a month, or not an Xfinity customer…