You shouldn't worry about falling out of the technology rat race. Everyone's stack is different, you would be lucky to time learning a technology with a particular job opportunity that is using it. You may as well just research it the weekend before the interview and be upfront about your ability to learn it.
You can't know every technology and in 5 years you will probably be applying for jobs with tech that doesn't even exist yet.
I'm not at all talking about knowing the latest tech when I say your skills may suffer. I'm just saying that in my experience, sometimes in a chill job your fundamentals as a developer can suffer. You can literally get worse at programming if you aren't challenged.
However, if you are an internally motivated and driven person, you can take that extra time and energy you get from the chill job and learn all kinds of things and become a much better engineer. The situation is whatever you make of it.
You can't know every technology and in 5 years you will probably be applying for jobs with tech that doesn't even exist yet.