Nope, this will never happen unless someone else picks it up.
Forge 1.12 is vastly different to any modern version, the mod would require a complete rewrite, using a completely different build system as well.
While it appears there's now ways to use modern Mixin and MixinExtras on it through MixinBooter, I don't even want to think about all the potential compatibility issues of all the coremods / ASM hacks that were so commonly used on 1.12.

So good luck to whoever wants to port the mod to 1.12 🫡

thank you for your reply , I want to thank the developer of ChatHeads for their contributions to the Minecraft modding community. Your work has brought joy to countless players, and your decision to focus on modern versions of the game is a reflection of your commitment to quality and sustainability. While the road to a 1.12.2 port may be fraught with challenges, the community’s passion and creativity ensure that the legacy of ChatHeads will endure.

To anyone considering taking on the task of porting ChatHeads to 1.12.2, I wish you the best of luck. It’s a challenging endeavor, but the rewards—both for yourself and for the community—are well worth the effort. And to the players who continue to enjoy Minecraft 1.12.2, keep exploring, building, and modding. The world of Minecraft is vast, and there’s always something new to discover.

Thank you, and happy modding! 🫡