One of the central hallmarks of mormonism is that they have a restored priesthood that includes a restored office of prophet. For mormons, the man who occupies the office of President of the mormon church is a true and only prophet of God on par with men like Moses, Isaiah and Jeremiah. The man who occupies that office today is Thomas Monson, a guy who has spent almost his entire life as a mormon leader. He was "called" as a local bishop when he was 22, which is pretty unusual. He has not had a job that wasn't connected to the mormon church for what looks like half a century, so this is a guy who knows mormonism inside and out. If you want to know something about mormonism, you could hardly find anyone who is better prepared to speak on the topic.
If you are looking for someone to prophesy though, you need to look elsewhere.
The mormon President is many things. Normally a good speaker, an outspoken believer, a spokesperson and a leader. But a prophet? Not hardly. You will look in vain for a prophetic utterance from Thomas Monson. Or his predecessor Gordon Hinckley. Or his predecessor. And on and on. In fact, other than the politically expedient "revelation" overturning the racist prohibition on blacks holding the mormon priesthood., the mormon prophet has not done anything prophetic for generations back. The Bible is allegedly not translated properly. Is the mormon prophet using his prophetic office and his "priesthood authority" to translate the Bible properly so mormons could trust what it says? Nope. They are apparently too busy appearing on Larry King Live.
When I hear a mormon talk about the "prophet", I always refer them back to Hebrews 1:1-2. We don't need prophets today to point forward to the Christ when Christ has already come and fulfilled all righteousness. We don't need a temple when Christ has made the perfect and complete sacrifice. We don't need a human priest to be a mediator for us when we have the great High Priest interceding for us directly to the Father.
Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these last days he has spoken to us by his Son, whom he appointed the heir of all things, through whom also he created the world. (Hebrews 1:1-2)