According to the MWI different outcomes to a decision are epistemic and metaphysical possibilities. At least I think they are - it is hard to say for sure without a definition of what the concept of "metaphysical possibility" refers to.

To explain what I mean, according to the conventional understanding of the MWI, the world splits. There are few pasts, and many futures. e.g. see:

http://www.hedweb.com/everett/everett.htm#do

http://www.hedweb.com/everett/everett.htm#split

Thus, from any starting position, there are many possible futures - and that's true regardless of what any embedded agents think they know or don't know about the state of the universe.