What happened to her father forbids even the thought of abdication! Her character and the way she has been carrying out her duties for over half a century shows this will NEVER be an option. UNTHINKABLE !
Of course you never know as it's not our decision when we have to leave this planet but keeping in mind her genes - and she inherited the physical strength of her mother - she might be around for many more years.
Will be interesting though to see what happens if the Duke has to go before her, if she can keep up with the demands and is still strong enough to carry on. Just thinking of it makes me shiver - her death is something I simply cannot imagine as she's been around all my life and I am sure many people feel this way.
So I am afraid Charles has to do what he has been doing all his life - keep on waiting and preparing