In theory, yes. But it looks complicated - just for having a link to our Threads account or having the Threads accounts of our users (nobody entered one in his/her user profile, yet) in the Clickable Social Icon Links on Profile theme component.
But thank you for bringing this up. I was not aware of this. And for sure it is something for “real own” icons which will never be part of FontAwesome.
For my use case and the Threads icon I will wait for FontAwesome 6 integration. 
Is there any rough time schedule/plan for that?