Really hard to comment on stuff like this as it depends upon the extent of his and the club's plans.
For instance, personally I'd be more than happy to see us finish well outside the top 6 if there was evidence of a root and branch restructure of the club. If the deadwood was properly cleared and replaced by young, talented, hungry, but ultimately inexperienced players to augment the young players we already have plus a handful of our current first team that deserve to stay and fit the profile in terms of age and ability. A year outside the top 6 next year, then top 4 the year after, and challenging for the title in year 3 would be absolutely fine by me. (I don't have any faith that Ole is the right guy to lead this, but we're talking hypothetically here, and I accept that I don't know for sure that he's not going to be a success)
If, however, Ole and the club decide they are not going to conduct a major restructure and are going to stick with what we have plus say 4 big-name signings then - given that he has already had half a year with the existing team - I would be looking for a top 3 finish. If he's way off that by Xmas then that is just not good enough.