The real threat to a senior IC, in my own experience, is losing their edge, especially in a large company. As they grow more senior, they will spend more time in meetings, writing more docs, aligning more teams, drawing more boxes, tossing around more terms, defining more product features, and talking to more customers. As time goes by, they gain more institutional knowledge and getting better at company dynamics. They know which VPs to trust. They know which squeaky wheels to oil, and which buttons to push. They do everything better, except designing or implementing a challenging system.
That is, the senior ICs start to resemble a strong product manager, or an effective director without a team. These are all good - until the company suddenly no longer needs them. Maybe their team has become a cost center. Maybe the project gets into maintenance mode. Or maybe the product has been so stable that the company does not even need more alignment. At that time, the ICs will find that all the institutional knowledge and so-called "leadership" is not that transferrable. And when they go out and interview for a new job, they find that they can't even sketch a solid design.
Sadly, I don't have a solution. There are exceptions. I guess it's natural that a senior engineer will gain breadth but also get distracted as they age. What they need is a different kind of depth. They can still be of value to a younger team if they are like a hard-science professor who depends on their PhD students to write papers, yet they can still advise the students as no one else. In industry, my role models are people like Michael Stonebreaker, who can still shape the architectures of modern databases in his 80s. Wernher von Braun of Saturn V rockets, who could come up with new rockets like no one else. Or Kelly Johnson of U-2, who could direct and unblock his engineers with ease. Or Marc Brooker of Amazon, who seems able to go deep into both database and distributed systems to keep coming up with amazing systems. But then, I'm not sure how many people can be talented as those engineers.
Or maybe another way is to get domain expertise, like how payment works, how insurance works, how accounting works, and etc?