I think that is what Prince Charles is hoping for in the future and the process has already begun; I think Andrew kept looking for rôles for his daughters but Charles has refused.
However, as long as charities, clubs and societies ask for their patronage, there will be a need for the services of some members of the RF..
The Duke of Kent, at age 84, still carries out many duties and travels as President of the Commonwealth War Graves Commission, of the RNLI, of The Stroke Association, of St Mungo's, of Endeavour, of sporting associations including The All England Tennis and Croquet Club, in fact 140 charities and associations.
Just because we don't hear reports of what other royals do on a daily basis doesn't mean they are not carrying out this work and attracting funds for the causes they represent.
These charities and associations may have to look elsewhere for their presidents and patrons in future.