I believe the Bible is God's word... kind of... I don't think it should be taken as literally "God's word!" like a lot of people do. I do think it was inspired by God, i.e. the writers were inspired to write it based on their experiences with God, but I don't think that God was actually guiding their hands on what to write. If He was then it rather makes Him look ignorant with all the contradictions that can be found in the Bible.
Now, as for prophecy, one needs to understand that prophecies (in general and not just in the Bible) are not by nature meant to come true. They are predictions based on if the current situation continues down the path it's headed. While I'm sure God CAN predict the future, to do so and tell us humans about it would be denying us the one of the most important things He gave us: free will.
As for that particular prophecy:
"evil slave that falls away and beats his fellow slaves because the master is delaying"
Anyone that understands human nature could predict that about any situation similar to the one described. When you have a group of people following a leader and that leader fails to lead and/or delays leadership, chances are someone in that group that has control issues is going to stand up and start pushing everyone to keep on going. Usually if someone has control issues of this nature they're going to push everyone way harder than they should (i.e. "beat" them).
Jesus' betrayal was another highly likely situation. Someone always tries to destroy a great leader and it's usually someone close to that leader. That's also still assuming that Jesus was the leader the Jews were waiting for. There was more than one "Jesus" walking around at the time who was rumored to perform miracles and was teaching similar concepts. There's even a conspiracy theory about Jesus' rise from dead actually being a hoax performed by one of his competitors that looked similar to him but never gained the kind of popularity he had.
Personally I feel that it is not important whether or not the prophecies in the Bible are "true" and "from God". If they are, there's nothing we can do to avoid them so we might as well continue living our lives and hoping for the best. If they are not, then they obviously are not of any importance at all.