I think this transfer will make or break Mourinho's reign at OT, if Lukaku flops he may well be gone. Obviously I hope it doesn't happen, but the spotlight will be on RL and Pogba in a big way this coming season and if United aren't making a serious challenge for the PL and/or making progress in the CL that might be that for Jose.
Sky Sports News just had a comparison of the stats from Lukaku and Rooney's first 6 PL seasons, RL comes out on top so hopefully he will kick on and flourish at OT in the seasons to come, I just think he needs to hit the ground running.