I built a really nice Minecraft: Java world in 1.16 but unfortunately the 1.17 update with the caves and new items will be coming soon. Can I somehow transfer my Minecraft world and regenerate the caves so that I can discover the new caves?
The caves in the chunks that you have already been to are not "updated" anyway, ie no new blocks or anything are created there.
You will only find new caves from the 1.17 update in caves that have not yet been generated.
But this is only a brief note.
I wouldn't think of anything so spontaneously how to transfer a world. But you could maybe copy the world a few times to be sure and see what happens or what changes when you open one of these copies with the new version.
So… I don't know that much about it either, but I'm pretty sure that there are various tools with which you can edit your world. Could I imagine that you can copy such an area and then somehow paste it into the new version?
You can copy certain areas. In addition, new chunks will be rendered in 1.17. It will take some time until the update.
