Reality is Bitcoin mining will ALWAYS be profitable, if it gets too costly hash rate goes down and profits per gh/s go up. It is fundamentally flawed to think Bitcoin mining could become unprofitable on the industrial scale.
The problem is it is up to their (cex.io) discretion which determines if it is unprofitable or not according to the terms people agreed to when signing up. Since it was a bit vague in that they gave no specifics, you are probably right in that they just made the decision which was most favorable to their self-interests.
To me the whole cloud mining didn't make a lot of sense in the first place. If these so called cloud miners were that profitable, they would simply keep it private and build their business up as the profits rolled in.