Hi,
it seems you can’t subscribe to a plugins’ asset store page to get a notification when a new version has been published. I couldn’t find that option at least.
Personally I find it quite useful to get such notification, so I wonder if users that purchased an editor extension would appreciate a “Check for Updates” feature for that particular plugin. It should be fairly easy to implement on the plugin itself though.
My idea would be to check for updates when the plugin window gets opened, once a day. An option to turn it off should be provided, as well as a button to check for updates manually. That’s what other software usually supports.