Honestly, I actually expected MMX to do a lot worse with sales. 71,000 debut compared to R&G's 38,000 debut. I suppose there was a lot more promotion with the wedding shock and it being a "secret book" at the time maybe helped too (and variants including Skottie Young and J Scott Campbell). But initially I thought #1 would be just under 50K at best. The drops are expected, 'Domino' and 'Jean Grey' had 70K to 20K drops as well, so yeah, it's done no better or worse than those satellite books.
I'd be happy if the series reaches 12 issues, which I think it will because the next arc should be about 5 issues (TPB length) which would make it 11 all up, and I think they'll sneak in another. On a personal note I will get what I was initially hoping for. None of us are naive enough to think this series would go beyond 25 issues, and even so, writers would probably move onto other projects by that stage.
KT did confirm seeding a Rogue storyline about controlling her powers, that could be another arc right there, and for Rogue's development, that's a big deal. So you never know...