I agree that Kolb was meant to be a measuring stick to know when EJ was ready to play, especially given that it was widely recognized that he was raw coming out of college. I think the coaches will give EJ every opportunity early on in the season to maintain the starting spot while Orton learns the offense, however if he falters I could see them going to KO as a stopgap, possibly in game if EJ is sucking it up, possibly for a game or two for EJ to get his head on straight.
My reasoning is: 1) the FO needs to win this season, or they're out 2) expectations on EJ are sky-high, and are likely to affect his play to some extent, regardless of how he appears to be embracing them 3) KO's play should be "overcomable" by EJ as he progresses if he really is going to be the franchise QB. Ultimately, I think KO gives the team the opportunity to have some patience in developing EJ in season while still maintaining some expectation of making the playoffs.