If he keeps producing like he is, and the fact that he is one of their best offensive prospects (Eldred the other) he is likely to stay up and if he is up, he will play, the only reason to send him down is to make sure he plays and gets plenty of at bats.
he should play at least 15 games behind the dish, and expect the pirates to try to move Redman and or Lawton, also remember that Mackoviak's flexibility really gives him more of an opportunity cause they can put Mack at 2nd 3rd or any OF spot. I think what you will see is him playing every game during IL, and prolly at least 5 games a week at C,1b,RF
just remember you heard about him from me first!
Next year he is a great sleeper who should get 150 games and qualify at C