I guess it's not decided yet.

On https://whattrainisitnow.com/release/?version=esr

We decided to extend support for ESR 115 only on Windows 7-8.1 and macOS 10.12-10.14 up to March 2025. We will re-evaluate this decision in early 2025 and announce any updates on ESR 115's end-of-life then.

Mozilla decided to extend updates only shortly before the Fx 115.16.0esr release as it was originally going to end at Fx 115.15.0esr. Since the extension was about six months, I would not be surprised if they extend updates again it will only be for another some six months.

Mozilla has supported the eol Windows 7, 8, 8.1 for two years longer from when Chrome/Chromium based browsers dropped Windows 7, 8, 8.1 back in Jan/Feb 2023.

I'm a retiree in my mid 70's...I've heard that Firefox will stop extending ESR's past March of this year. I'm not in a position to buy and update all my software and laptop & desktop the latter can't go any higher on Mac OS. So I'm asking that you please consider continuing support for older browsers. My browser is Mac Safari 14.1.2, I would be OK making a good sized donation to Mozilla or paying a monthly subscription if necessary to be kept updated on Firefox ESR's. I've seen other inquiries on your site from others asking about the same thing. So please consider my request and let me know if there's anything I can do to get your continued ESR support for my computers. It would mean a great deal to me and I know quite a few others as well...So please pass my thoughts up to management and I will hope for the best...

After review it was decided that support for those platforms on the ESR 115 branch will be extended for another 6 months through September 2025 with the final planned release now being version 115.27. We will again review this decision as we approach the new deadline to determine whether further extension is warranted at that time.