City have opened up a 12-point lead at the summit thanks to a run of 14 victories in a row, putting them well on course for a third title in four seasons under Pep Guardiola.
Keane does not expect any change in terms of the top two, but he has questioned Leicester and West Ham's ability to hold on for a place in the top four.
"Over the last week, you'd look at Leicester," he told Sky Sports News. "They obviously messed up last year when they were in a great position and they've now picked up one or two injuries.
"[Harvey] Barnes is injured. [James] Maddison is struggling. I know they've got a nice little cushion, but you'd worry for Leicester and West Ham, when you think if Liverpool can go on a roll, can Everton pick up some results, and obviously Chelsea.
"But you'd expect Man United and City to be the guaranteed top two."
United travel to Crystal Palace for their next league outing on Wednesday, while Man City are at home to Wolverhampton Wanderers the day before.