Jupiter and Jupiter X are two different themes. The Jupiter X theme was reborn from Jupiter, but it uses Elementor rather than WPBakery Page Builder, so it works differently. Even still, Jupiter receives maintenance and security updates and is available on ThemeForest in the same package. Follow this article for more info:
How to download Jupiter v6 theme
Jupiter 6 is supported and will receive lifetime updates. You don’t need to move to Jupiter X if you are happy with Jupiter. We recommend moving to Jupiter X only for your new websites.
Note: Jupiter X doesn’t require Elementor Pro version as it has many additional features and some built-in premium plugins which help creating a website.
You won’t need to buy a separate license for Jupiter X and still, you can benefit from the Jupiter legacy version as well.
What changes were made to Jupiter X and how it differs from Jupiter V6, you can find this article.
We provide Jupiter 6 to Jupiter X migration service under Content Management service in WPDone.
Updating from Jupiter V6 to Jupiter X
As for the update process, you have to upload Jupiter X to your website as a new theme. Read this article to find how to install it. It’s required because Jupiter X has different functionality and features like new page builder.
Note: We will release constant updates and support Jupiter V6 as we do for Jupiter X. You can continue using Jupiter V6 for years.