Sorry I couldn't write more about the traditional format, I had to dash off for a short holiday. But I've had some time to think about it a bit.
Like Kitty said, the 20 year pattern is kind of expected. It's generational and it's good for each generation to get their "version" of it. But there's something else Astroboy does with each incarnation, and that's ground-breaking animation.
The 1963 series was one of the first anime series ever (I think Instant History beat it by a year or two) and even though some of the animation looks a bit janky, there are also some cool moments where they did some expensive looking parallax background animations. So many new techniques were pioneered.
The 1980 series had fantastic animation for its time. Visually it looks a decade ahead of any western kids' cartoon, and most other anime as well. There's virtually no sign of the "Hanna Barbera effect", where the foreground characters don't match the background art. Episodes dealt with climate change, self-identity in cybernetics, morality in AI, etc. Advanced stuff that's still relevant decades later. Even the futuristic architecture doesn't look terribly dated.
The 2003 series had some of the most expensive production costs of any anime series. Computerised layout (I assume since I never saw any cels from it) and visually it still holds up today.
So as far as production value goes, there's no "typical anime" version of Astroboy. It's all been top quality stuff. Astro is such a cultural icon I can't imagine the Japanese making it second rate. They do have the technology to make something better now (4K, maybe rotoscoped CGI like Appleseed which would also allow for higher frame rates) but the 2003 series is still solid. So I think kids now can watch the 2003 series and still think of it as modern. There's no rush to bring forward another generational retelling yet.
In the meantime, making non-traditional versions is a great idea. It's a well-loved anime, spin-offs in general are popular, and they're splitting it into different age demographics. Now we just need an anime of Urasawa's Pluto.
I would expect to see a 4th traditional retelling in maybe 5 ... 10 ... 15 years from now. They're not going to discard the original stories of such a major cultural icon, especially as we move into real life issues of emergent AI. Astro has been a strong bridge between humans and robots in sci-fi, and I expect that'll make him a relevant icon in years ahead. Maybe we can ask an AI to direct it from the perspective of a robot.