Is it possible that you may one day regret choosing to not have a child? Yes, of course.
It's also possible to regret having children. That's why subreddits like Regretful Parents and Facebook groups like "I Regret Having a Child" exist.
People don't like to admit it but some people do regret having kids. People can only make the choice that they feel is right for them at the time. You can't make the choice to have a child based off a fear that one day, when you're old and grey and your "best" years are behind you, you regretted not doing so.
There's been studies that have shown that this regret at choosing to not have children simply isn't common or prevalent. Lots of people love to throw out the old, "What about when you're older?" bingo remarks at us child-free people, but don't seem to realise the intrinsic selfishness of such remarks.
Having a child in the hopes that they'll keep you company in old age or even be your carers when you need them is selfish and the wrong reason to have kids. I hate seeing this comment and it's been voiced a couple of times by a couple of different PP's because it makes no sense.
Doing something to stave off potential future regret is stupid. Especially something as big as having a child. There's a saying around that goes "I'd rather regret not having a child than regret having a child."
Of course, it's something worth considering and thinking about what your future will look like either way and imagine how you might feel. Truth is, none of us can know or predict the future. Regret also isn't a be-all and end-all emotion. Everyone regrets something because we can't take every path that is available to be travelled. We have to make choices and that means some things we won't get to do or experience.
Let's say OP did get to an age where she started to question and regret her choice and it's too late to go back on it-she can deal and work through that regret. If she's young enough or capable, she can volunteer or maybe she has children in her life from relatives or friends.
Also, nursing and residential homes are full of people who had children and many of those adult children never call or visit. So many care workers have voiced this observation of people, who have rooms covered in pictures of their children and grandchildren and they never get visited by said children/grandchildren.
So, it's not a guarantee for company or care.