What happens after the Datylon for Illustrator license expires?

No work is lost when your Datylon for Illustrator trial or subscription expires.

The expiration or even uninstall of the Datylon for Illustrator plugin does not affect the Datylon charts in your Illustrator documents. They only cannot be edited anymore as Datylon objects. In case the Datylon charts are not expanded, the data and the charts themselves can still be edited later with a valid Datylon for Illustrator subscription.

When your trial version or subscription of Datylon for Illustrator expires, and even without the plug-in installed, charts created with Datylon can always be manipulated in Adobe Illustrator as regular .svg objects. You just can't use the Datylon features and functionality. All charts can be viewed, moved and scaled, or exported just like any other .svg object at any time.

However, after expanding and ungrouping the chart, the link with the data is lost and can never be retrieved.  See this article for more details about ungrouping a Datylon Chart.