Canonical is improving Ubuntu Touch with each new version, but it seems that a number of problems have been forcing the developers to stop promoting images for the users.
The Ubuntu team promoted an image just a few days ago, but it seems that, since then, there have been a few problems that stopped them from doing just that.
“We had multiple images over the week-end, those contains minor changes. Partial results on the maguro images which is preventing us to take a release decision on image #149.”
“Some random crashes on Unity8 which are not reproducible after rerunning a lot of them. So, this topic is on the radar (we'll have a look as well at tomorrow's image results),” said Didier Roche on the official mailing list.
This is where the Canonical automated tests for Ubuntu Touch really made a difference. Users don't get untested images, but this also means that updates will be only released when developers think it's safe to do so.