I can't say any specific one will be as advertised at all.
However, due to the quantity + odds of reaching potential means that it's pretty much guaranteed that we'll have some good players.
Look at this list of our outfielder prospects. All of them have the potential to be MLB regulars or better. Lets say only 1 in 5 actually reaches their potential.
Dwight Smith, Anthony Gose, Jake Marisnick, Jacob Anderson, DJ Davis, Anthony Alford.
While it's unlikely that all of them become regulars or better, one of them at least should. With a long term player already there (Rasmus) that means we only need a second guy to hit his potential, or conversely find another guy who is decent.
Similarly with the pitchers. We have about 15 good pitching prospects, so if you do that 1 in 5 thing, that's three rotation spots filled and that's not counting Romero, Morrow, and Alvarez.
That's why I'm not worried.