So just to conclude this, Portnoy stated it about Yes, Rush, Maiden, Metallica but it was less of an official statement and more of a Portnoy musing ? (not meant negatively on Portnoy if it came out that way).
I don't think it was him musing so much. Given that the majority of the band are all fans of Rush, Maiden and Metallica and the bands all have much bigger audiences that might be interested in DT's music, I believe they all would be interested in going out on tour with them.
In fact, they were supposed to take the summer of 2010 off, but when they were offered the chance to open up for Maiden, they gave up their break so that they could go out on the road with them. So it wasn't just simply a matter of MP thinking out loud.
Put it this way: if Rush were to offer DT an opening slot on a tour in 2016, you can bet your bottom dollar that they'd take the gig, no questions asked. Just look at JP's WWRD mentality and how his inner fanboy was on display when he and Geddy Lee were both on Eddie Trunk's TV show. I'd bet the same thing would be true if Metallica were to offer them up an opening slot too.