I have been telling people that, titles aside, senior developers were the people not afraid to write original code. I don’t see LLMs changing this. I only envision people wishing LLMs would change this.
1) Senior developers are more likely to know how to approach a variety of tasks, including complex ones, in ways that work, and are more likely to (maybe almost subconsciously) stick to these proven design patterns rather than reinvent the wheel in some novel way. Even if the task itself is somewhat novel, they will break it down in familar ways into familar subtasks/patterns. For sure if a task does require some thinking outside the box, or a novel approach, then the senior developer might have better intuition on what to consider.
The major caveat to this is that I'm an old school developer, who started professionally in the early 80's, a time when you basically had to invent everything from scratch, so certainly there is no mental block to having to do so, and I'm aware there is at least a generation of developers that grew up with stack overflow and have much more of a mindset of building stuff using cut an paste, and less having to sit down and write much complex/novel code themselves.
2) I think the real distinction of senior vs junior programmers, that will carry over into the AI era, is that senior developers have had enough experience, at increasing levels of complexity, that they know how to architect and work on large complex projects where a more junior developer will flounder. In the AI coding world, at least for time being, until something closer to AGI is achieved (could be 10-20 years away), you still need to be able to plan and architect the project if you want to achieve a result where the outcome isn't just some random "I let the AI choose everything" experiment.