Sales-wise, it's only selling a measly 21k+. I know that doesn't sound great. However, that more or less puts it on par with Avengers Academy. New Mutants also sells more than Secret Avengers, Thunderbolts, and Journey into Mystery. On top of that, last month, it lost only 0.78% readership (167 issues). JiM's last issue dropped by 3x that many. A series like Astonishing X-Men sells more, but it's also seeing far sharper decline than even that. Last month, Astonishing lost ~17x as many readers or 8.47% of its readership. That's a drop of 2897 readers compared to New Mutants 167 drop. All things considered, NM is stable by comparison.
Not saying that New Mutants is safe. It ranks pretty low on the top 100. It's quite possible that it's in danger. Still, we have no idea what the post AvX status quo will be and how the books will be affected. Also, if recent rumblings over a New Mutants movie at FOX turn out to be true, you could easily see Marvel make a bigger push to try and position the book to jump up in the charts. Not saying that that's going to happen either. However, not one of us works at Marvel. We can only guess.
The way I see it, cancel New Mutants today and it'll be back in short order. It's one of those titles and concepts that's just impossible to get rid of. New Mutants morphed into X-Force. Then they morphed back into the New Mutants, except as teachers this time. Now they're back as their own team. Given that New Mutants was the very first X-Men first spin-off series, it's a hard title to totally bury.