Does anyone know when the next time tatsugiri will be in a raid?

I'm trying to collect all 3 types of tatsugiri.
I don't have anything worth trading at the moment nor am I at that high of a friendship level with anyone to do remote trades.
So the only real way for me to get them is thru raids, I'm not just sure if/when they will be back in raids.

Any information on when they will be in raids again is much appreciated!