With MWI, this is incorrect - we do predict the outcome: all the branches.
The MWI gives an illusion of predictability ("Everything possible happens! We just don't see it because nearly all of it happens somewhere else to some other 'us'!"). Unfortunately, it can no more answer the question of which outcome an experiment will measure in "this world" than any other interpretation.
Even more unfortunately, and at a risk of a massive downvote, I hate to say it, but the MWI has become an official LW religion:
proclaimed to be true true by the founder: check
provides comfort to the masses: check
sets the group apart from others: check
impossible to falsify: check
makes one feel superior because of "deeper understanding of the world": check
Quantum Mechanics is falsifiable; MWI vs Copenhagen is mathematically equivalent. I'd call it a preference rather than a religion.
[edit] Poster below states that they're not mathematically equivalent. I think a better way of saying it is "MWI is related to Copenhagen so that observable evidence for or against one is always and exactly observable evidence for or against the other as well. "
Suppose we had a model M that we thought described cannons and cannon balls. M consists of a set of mathematical assertions about cannons, and the hypothesis is that these fully describe cannons in the sense that any question about cannons ("what trajectory do cannon balls follow for certain firing angles?", "Which angle should we pick to hit a certain target?") can be answered by deriving statements from M. Suppose further that M is specified in a certain mathematical system called A, consisting of axioms A1...An.
Now there is much to be said about good ways to find out whether M is true of cannons or not, but consider just this particular (strange) outcome: Suppose we discover that a crucial question about cannons - e.g. Q="Do cannon balls always land on the ground, for all firing angles?" - turned out to be not just un-answerable by our model M but formally independent of the mathematical system A in the sense that the addition of some axiom A0 implies Q, while the addition of its negation, ~A0, implies ~Q.
What would this say about our model for cannons? Let's suppose that we can take Q as a prima facie substantive question with a definitive yes or no answer regardless of any model or axiomatization. At the very least it seems that M must be an incomplete model of cannons if the system in which it is specified is insufficient to answer the various questions of interest. It seems to me that
If a question about reality turns out to be logically independent of a model M, then M is not a complete model of reality.
Now we have an axiomatization of mathematics -- let's say it's ZFC for now -- and we have a model of computation in reality, which is M="The unvierse can contain machines that (efficiently) compute F iff there exists a Turing machine that (efficiently) computes F" with appropriate definitions of what exactly a Turing machine is in terms of ZFC. Suppose we want to answer a question like Q="Can the universe contain machines that efficiently solve SAT?"
Under the premise that M is true, the question Q becomes the pure logical question R="Are there Turing machines that efficiently solve SAT?", i.e. the P versus NP problem.
Now suppose that R was shown to be formally independent of ZFC in the sense that for some axiom A0, ZFC+A0 implies P=NP and ZFC+~A implies P!=NP. This would resolve the mathematical question of P versus NP but the question Q seems like a prima facie concrete question with a definitive yes or no answer that does not rely for its substance on M or ZFC or any other epistemic construct. It would seem that we must have missed something in our description of reality, M.
Perhaps more controversially, I claim: Under the correct model M' it seems that it's impossible for a substantive question (such as Q) to be unanswerable.
All this adds up to: The P versus NP problem (and questions like it that can be phrased as definitive questions about reality) must have an answer unless our model of reality is incomplete.