City lifted the FA Cup and also qualified for the Champions League for the first time last season and are expected to embark on another spending spree this summer.
Johnson said: "United have been on top for decades now. But I think we are definitely closer.
"I think we are probably as close as we ever were. I think everyone knows that now.
"Maybe if you tweak the squad a little bit, we could give it a massive push next season, and who knows, it could all change."