To put things in some perspective, Trout's WAR last season was a mind boggling 10.7, which is tied for 20th best of all-time. The guys ahead of him on that list are names like Babe Ruth, Barry Bonds, Mickey Mantle, Willie Mays, etc... And those were years they were having in the prime of their careers. So it's unlikely we'll ever see another guy come out of a nowhere like that and have THAT kind of season probably again in any of our lifetimes.
That said, if you're looking for a deep sleeper, my money would be on Myers, Oscar Taveras in St. Louis if they make a move to open up an OF spot, or Jackie Bradley in Boston if they decide to move Ellsbury.
I guess if you're looking for someone a little more well known that probably won't go undrafted but has a chance to make the leap into stardom this year, I would take a long, hard look at Manny Machado (Orioles), Anthony Rizzo (Cubs), or Salvador Perez (Royals - bonus, he's a catcher).