The question is not “is something going to go seriously wrong, or not?”
The question is if you are prepared to deal with it if it does. Horses are a risk regardless, although you do know of something specific with this one.
Because you mention your own age, I gather you have an extra layer of concern for the long-term future. I would just assume that a potential downside is part of the package with any new horse. Only you can decide if you are prepared to deal with the downside, financially, resources, emotionally, etc.
In your shoes I would approach the cervical issue as high risk, average risk or low risk of being a future problem. And I would define how bad the worst case would be, to know if I were prepared for that. But of course something totally unknown at this time could go wrong and that’s part of horse ownership for all of us to prepare to handle.
Also because of your mention of your age, your post sounds as if you are pondering if you want to be a horse owner at all after your current horse. It’s kind of like adopting a kid when you are 53 years old (ok maybe not as intense re daily life - or maybe it is?). You may be the perfect person to do it! But of course you will have the responsibility for the next one or two decades, whatever happens. And you do need to spell out a fallback plan if you can’t continue to be the active horse owner for health reasons. That won’t necessarily become an issue, but the your own risk is higher for the future, of course.
That’s what I sense is part of your question. Maybe it will help to quantify it in this way? High/average/low risk preference, and ability to deal with worst-case and even intermediate-case scenarios, financially and otherwise.
Good luck on your journey! 