i think it’s cool to keep the jam version available and left the way it is for posterity.
- a separate project page for a post-jam version is nice if you have an html build for both. that way each can be played online without having to download them. you can link to other version in the description on each page.
- itch does allow uploading multiple files to a project page, so you can use the same project page for the jam and post-jam versions. i did this with my first GBJam game. i also posted a few dev logs with some art that didn’t get used and just talking about the jam version and stuff.
ultimately it’s up to you what you would rather do. not everyone keeps the jam version available.