I am not sure about installations that have been made via file by the beta testers.
For users of the existing marketplace extension it should at least get displayed as an available update from the extension tab.
But I think I have also seen some kind of prompt for other extensions in the past.
I will install the beta an test it myself.
Anyways I will of course add a post here or maybe some announcement thread in the category to inform more people about the possibility to Check for updates. 