@remi I'm 50, and I've remained an "IC" and never moved into management. Actually I did run my own business for two years when I was 21 and although it was reasonably successful, I hated every minute. Never again!
How do I pick up new fields? I dunno - I just sit down and start typing. I started as a graphics programmer, moved into animation middleware, then hardware and instruction set design, then everything to do with VR, now back in graphics software. It's all over the place.
@remi The key is to remain curious in your side hobbies and keep gathering general understanding. That way, if a new topic (or new job) comes up, you have a basic framework to start diving into. "Smart guy one level deep" is a bit of a notorious menace, but it's still better than no knowledge at all.
5-year plans are fine. Don't expect to stick to them.
"Plans are worthless, but planning is invaluable."
But also:
"I am a great believer in luck. The harder I work the more I seem to have."
@remi The other key is learning how to work well with others, especially younger angrier folks, even if (a) you could do the job quicker than them and (b) they're irritating antisocial arrogant little shits.
You don't necessarily have to actively teach them, but you can "lead" by example and be a smooth operator, not a sharp annoyance. Some people (and technical issues) are not your problem to solve. Learn to be OK with that.