Not even close.
30 years of programming and my best code has always been my most recent. I just keep getting better and better with no end in sight. And I love it. As far as I’m concerned, there’s absolutely no reason to believe the hypothesis of peaking and declining. Not me, that’s for sure, and not most of the people I know in their 40’s and 50’s.
In this way, we are “not” like athletes at all. I remember watching Michael Jordan when he played for the Wizards, riding the staionary bike to keep loose during timeouts. What a pity, I thought, to be at the top of your game, then a shadow of yourself just 5 years later.
We programmers are not like that. Just take care of yourself and you don’t have to level off until you would have anyway. All the new technology and opportunities keep the field fresh. And the people, too.