It's interesting because, common sense would indicate that a backup plan is a great idea. However, most pro athletes and elite persons in any field, usually are intensely focused on thier one and only goal. Including most that are quite successful. It almost seems like if you aren't born with virtuoso talent, you are best served to go 'all in' at your primary goal. Any amount of time considering or preparing for some back up alternative is taking away from time and effort that can be spent on achieving your primary goal. In other words, counterproductive.
On the other hand... MOST (seriously, pay attention for just a second) MOST MOST MOST people who desire to be at the top if a very exclusive field never get there. And there are innumerable reasons why:
Lack of: will, talent, developed skill, good luck, confidence, mental strength/stability, understanding of real requirements to accomplish goal
Too much: bad luck, injury/illness, stiff competition, unearned overconfidence;
And there's plenty I'm probably missing.
Here's the deal. You will never know for sure unless you go for broke and have ALL aspects covered. most impprtant beimg will. HOWEVER, you will likely (if you know the true, real numbers of failures in this field vs. successes) fail. Again. YOU WILL LIKELY FAIL.
So it's probably a good idea to have a backup plan in place.
Good luck!!! I want to see you do it.