Johnson's name has certainly come up to replace May, but I still see him as a long shot particularly since hard brexit just had its legs kicked out from under, and it's pretty clear the DUP won't stand for a hard border with Ireland.
As for Rob Ford, he only won the one election for mayor, (eventually) sidelined by Council after the crack scandal broke, and had to withdraw shortly after declaring for reelection due, as you said, to health reasons.
His brother Doug ran in his place, and lost decisively 33% to John Tory's 40%. Small consolation since Tory has carried on with the core Ford executive committee and downtown-unfriendly policies, The amalgamated city is riven between downtown and suburban factions, with the "tax-and-spend" downtown consistently out-voted on key issues related to civic quality of life and the funding necessary for it.
EDITED: 12 Jun 2017 12:28 by DSMITHHFX