Missed his chance during Marineford. Shanks easily let Teach go just like that.
The whole "unable to trace him" also doesn't sound believable. It is pretty clear imo that Shanks didn't bother to actually looking for Teach.
If whole "BB grows stronger and beat Shanks" theory is true, it just feels dumb on Shanks' portrayal. He is just passive, although already knowing the destiny and potential danger in Teach, and just quietly waiting for his defeat.
Thoughts? @GalaxyLevelShanks @Shiroyru
Why has Shanks not attacked Teach in Hachinosu but has shown intent to attack him in Wano? Well that's clear proof Shanks isn't scared of Teach but isn't pulling up to his territory because he knows it's going to be a defeat if he fights Teach with Home Court Advantage. And we know Shanks values the people he protects over everyone else so if he attacks without all of Teach's commanders being in Hachinosu, his territory might be fucked.
As to why he didn't trace BB after Marineford? Well you can chalk that down to Shanks wanting to maintain peace (it would be hypocritical for him to gun down someone right after preaching about stopping a war) and having to take care of Ace/WB's funeral.
But between Rocky Port and Marineford... idk man. It makes no sense why he didn't try tracking him down. He's tracked Kaido and stopped him. So either it's:
1) Teach is just
that sneaky that he can't be tracked by the RHP intelligence
OR the more likely option:
2) PIS. Shanks vs Teach is supposed to be an endgame fight and it makes no sense to have it happen so early. He's restricted by plot hence why he didn't help Ace track Teach down despite being on friendly terms with him.
OR the least likely option:
3) Shanks vs Teach won't happen.