Doing the job better, I have no idea over how I don't know your quality of work beyond the anecdote of that student or whatever. He could end up a better person for the job for all I know with some on-site training if he has the right mindset and potential for it.
Getting qualified or smooth talking his way in though? That's completely variable.
Without 20 years, or with 20 years?
Your focus on 'may' though has me inclined to say yes, as it's still within the realm of possibility. It's not like your job requires having an extra digit or something right?
I guess I was mostly asking because I didn't understand what you meant. If he's saying that, given 20 years, he may be able to do my job better, then I don't really have much issue with that. Although, I'm not convinced it is necessarily true.