I, HyperSpeeed/ThexXTURBOXx/Nico Mexis, have made the decision to not port Reforged to 1.13.2 and beyond.
HOWEVER I have done something much better than that:

I have ported the original Balkon's WeaponMod to 1.7.10 (with fixes and visual changes), 1.8.9, 1.9.4, 1.10.2, 1.11.2, 1.12.2, 1.13.2, 1.14.4, 1.15.1, 1.16.5, 1.17.1, 1.18.2, 1.19.4, 1.20.6, and even 1.21!
The port (now-called Balkon's WeaponMod: Legacy) was basically already finished a few days ago, but I decided to not post it until 1.21 is officially released.
And since today was the day: Here we are!
Currently (as of 21:28 GMT+2), the mod is under review on both CurseForge and Modrinth.
The source code is already available here.

So, just keep an eye on both CurseForge and Modrinth and be one of the first to try it out!
I have tested the basic functionality on each version (which took a LONG time), but there are still probably some bugs to squash.
Feel free to report everything you find here!

And without anything further to say, enjoy! (^_^)/

That's great news. :D