Nothing's been sent out yet, but I hear they might start teasing a little more leading up to the announcement. Today they mentioned the 2013 site again on their Facebook and Twitter pages. They've been a lot more reserved about it than DW, but then again, they really haven't needed to say anything to get the whole world talking about SDC. So far this is the top ride of 2013 next to CP's new B&M, but I think this one is more exciting to watch, and will probably be a more exciting ride even.
Haven't heard anyone else mention a tunnel... if it were able to be spotted from the train I think Swoosh or chadster would have spotted it by now, but there are so many secrets this ride still holds that I am hesitant to make any more speculation as to what it may or may not have. We've only seen about a quarter of the layout so far at best.