Mormons are pretty certain folks. They are absolutely certain about lots of stuff. Just read any conference report and you can make a long list of absolutes. Add in the faith-promoting-rumors and the list gets even longer.
The trouble with absolutes is that they are rarely absolute. Never and always are very long times and make fools out of most absolutes. Everybody is a pretty large group. To say that something applies for everyone is asking to be shown wrong.
At various times Mormons and their leaders have been absolutely certain about many things that turned out later to be wrong. I'm not so much into rubbing anybody's nose in the past so I leave it to you to make the list of wrong predictions. In fact, history shows that God seems to enjoy making exceptions to rules that folks thought were absolutes.
I'm not faulting them for being wrong. We all make mistakes and we all believe things that later turn out to be false - that's life. I'm just saying that I don't see much evidence that the LDS church is better at predicting the future than anybody else.