Tim:
Didn't you read the page on link you quoted?
"Thunderbird version 78.0 is only offered as direct download from thunderbird.net and not as an upgrade from Thunderbird version 68 or earlier. A future release will provide updates from earlier versions."
SternData:
Yes, I read it. Will Thunderbird continue to be part of the Fedora repos?
You're asking the wrong people that question. But I interpret their statement as *that* release cannot be installed as an update (it can't import prior settings/data), but that in the future improved version will have the ability to be installed as an update (they'll build in an import feature), so hold off until you see that announcement.