Installing over an older version no longer makes MiKey vanish from the input menu: the installer waits until macOS is done with the old copy, then registers MiKey and checks until it stays listed.
If MiKey was the active input source, it still is after the upgrade.
Already on 1.0.1 and lost MiKey? Install 1.0.2 over it and it is back.
macOS: after installing, MiKey shows up in the input menu right away (on a new Mac it used to appear only as an app, and as an input source only after logging out).
The installer always installs into /Library/Input Methods and removes an older MiKey copy in the user folder.
Logo and links in the menu bar app: MiKey instead of Vikey.