I find it suspcious that the press release would say, 7 brand new lv.X and then say (including mewtwo) when Mewtwo is coming out in the tin. Could that mean that the tin lv.Xs will be numbered in the set and that there will only actually be 5 other lv.Xs in the set? Could that mean that the Mewtwo lv.X in the set is alternative art? This is what I think will happen.
We will get 7 lv.Xs in the set. 2 will include alternative art of Rhyperior and Mewtwo lv.X and 5 othr lv.Xs. We will then get the 2 tins with the original art Rhyperior lv.X and Mewtwo lv.X in them. I think that makes the most sense.
Let's play devil's advocate though. What if the lv.Xs in the tins are the same exact cards as the ones in the set? Take about a loss of value. Didn't pull a Mewtwo lv.X in your box? Go buy a tin and complete your set. Oh you pulled 2 Mewtwo lv.X in your box? Great, they are worth a whopping $15 each. Nah, that wouldn't happen.