If you're on Windows or macOS and want to upgrade to Thunderbird 115 right now, you don't need to wait for the auto-update.
Just download the installer at https://thunderbird.net, and install it over your existing version. This is effectively a manual upgrade from 102 to 115.
If you're using Linux, well, it gets more complicated... For now, we recommend waiting for your distro's maintainers to send it your way. Or wait for our Flatpak release, which should happen very soon.