Your natural reactions have been honed over the years to manoevring autos and you'll be OK right foot braking when you're 80. Mind you, you'd be better off learning to left foot brake when manoeuvring while there's still time!
The nature of the problem changes if you take a typical 70-80 year-old responding to unanticipated events, driving a vehicle with unfamiliar foot controls in a crowded place. He has to unlearn a key part of his 50 - 60 years of driving experience every time he gets behind the wheel and in an emergency will do what comes instinctively and when that doesn't work, he freezes up!