I found this interview with the Mayor on Youtube. If you move the slider to 2:20 he says of Boris Johnson “I don’t believe he will keep the pensioners’ travel as it is”.
The Mayor knows full well that the Freedom Pass is administered and paid for by the London boroughs and that he has nothing to do with it beyond, bizarrely, having the power to impose an agreement when the London boroughs are negotiating with their supplier TfL of which he is the chairman. This arrangement is called the reserve scheme. It has no parallel anywhere else in the country.
Bors Johnson says: “The Freedom Pass will be protected as an untouchable right for London pensioners.”