I have that theory that Teach will force Yamato on his crew and that's how Yamato will meet up with the SHPs.
How? You may ask.
Teach goes to Wano, claims Pluton. Yamato offers Teach to join him if he leaves the Capitol and the island alone. Teach agrees.
I think something similair will happen to Loki post Elbaf and that's how Loki and Yamato will end up on Lough Tale when Luffy and Teach meet.
Also fun fact: If that were to come true and both Luffy and Teach meet up...that would be the day where all major races in One Piece would be united at one place for thge very first time. Mark my words. It's too relevant for it to not happen.