18 from the next twelve fixtures seems incredibly optimistic, looking at them. We would have to beat Leeds, get something from the brutal run that starts up immediately afterward, and win at least three of the last four prior to the break against the league's weaker sides.
As a practical matter, if we're out of the relegation zone prior to the break I think he will be allowed to continue. Away to City is a lost cause, but I would feel good about getting four from the two home fixtures over Christmas and New Year's. Then, he has the rest of the season to sort it out. The schedule in the second half is a lot kinder than the first half, with us hosting many of the probable midtable sides, able to get something from the probable six-pointers away and having only one rough three-match stretch in the middle.