I think he can take us to a stable top-10 position, but it's very rare that any manager can take a club from lower positions to CL football on their own. The managers that do deliver CL football have years of experience from other clubs, other top leagues, experience of equivalent top-flight european football from more than just one club. They tend to come into an established top-10 club and take them to the next step. There are exceptions of course, such as at Chelsea, but the work there was done before Di Matteo came along.
IMO, our next step is an established top-10 position and then we will change managers again.