I am looking forward to have version 115 but flatpak package is not updated to version 115 instead, it shows old version 102.13.0. When will the flatpak version will receive the latest release?

Work is in progress. The answer is, simply when it is finished.

I just ran `flatpak update` and now have Thunderbird 115.0.1.

Caution: If you use the Provider for Exchange ActiveSync and TbSync add-ons have not yet been updated to work with 115.x and will be disabled if you upgrade. (Well, I'm stuck until that's sorted out. Ugh.)