I've been monitoring Jacob Turner very closely as well, and stated some of my opinions and quoted some articles in that thread. While I thought he was very close, I have a feeling, based on statements made by the Tigers brass, that we won't see him this year. Turner has thrown a lot of innings this year, and it has been suggested by the Tigers that his innings are going to be limited. If he is the Tigers' #5 starter, they aren't able to do that as well as if he stays in AA. He also has been struggling recently which means he could be fatigued from the innings.
IMO, it will on depend on whether or not the Tigers acquire a SP at the deadline or not. If they don't, Turner odds of coming to the bigs increase significantly. But if the Tigers are able to get a guy like Kuroda, Lowe, or Guthrie then I don't think we will see Turner until 2012, even if there is injuries the rotation.
EDIT: Although it should be mentioned that the Tigers altered Turner's rotation spot and he is now lined up with the Tigers major league #5 rotation spot. Turner was given 10 days rest since his last start on July 15 [mostly due to the futures game/allstar break], and just pitched today for Erie [8 IP 7H 1BB 3 ER 8 K] and Duane Below is pitching for the Tigers tonight as well.