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. 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.

If you want to edit the charts when your trial version or subscription of Datylon for Illustrator expires, or even without the plug-in installed, you need to expand the charts in Illustrator (Illustrator menu > Object > Expand).

However, after expanding 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.