Yes, you can revoke a link at any time; revoking deletes the published data. For a dashboard's stable link, that is the dashboard and every revision kept under it.
Revoking does not delete the dashboard on your machine. Publish it again and Emolysis makes a new link with a new URL; this is also how you change who can open a dashboard.
Expiry is for snapshot links. Charts published on their own, rather than as a saved dashboard, get a snapshot link, which can have an expiry date after which it stops working. A dashboard's stable link has no expiry date.
Someone who opens a revoked or expired link sees a page that says so, without any of the data. The person who published it, and their organization's owners and admins, can revoke it.
Copies people made while a link was open, such as screenshots or downloads, are outside what revoking can reach. Choose the visibility setting with that in mind: see who can see a shared dashboard and the sharing docs.