Iron Maiden have a ton of albums, but a lot of them are just so-so. Had they waited say 3 or 4 years instead of 2 per album, maybe the quality would have been better? It seems like in the 90's, they pretty much just walked into the studio and whatever happened, happened. Blind Guardian is another band that takes at least four year in between albums but they usually come out amazingly. It seems like most bands over the last 10 years or so really enjoy taking their time with albums which is pretty much the opposite of how it was in the 80's!
Edit: I really have a feeling that the new SX album will be out before June but of course I could be wrong. My guess is that they are finishing the mixing now and then won't really promote it too far in advance to avoid a leak. Then again, I don't really see them randomly just one day posting something like "The new album is out now, bye".