Hmm
It's possible
It's either that or Shamrock is killed by Teach and his fruit is taken by him.
Or Shiryu manages to steal his sword or kills him for it after Sabo weakens him.
Oh, right. I almost forgot the very old fan theory of Blackbeard having the Cerberus devil fruit or hippo, the famous association with the number 3.
Well, I guess it's not out of this world. Darkness + Cerberus would also fit.
Shiryu is an interesting candidate for another "power-up" (devil fruit sword). Since many people currently don't buy him being able to give Zoro a good fight, this could make up for it a little.
The invisibility is good and all but something to increase his striking force would be nice. Let's see, since the Blackbeard Pirates are most likely going after the ancient weapons. Anyone with a devil fruit that's in Wano or on Fishmen island is potentially at risk of getting their powers stolen.
And it doesn't have to stop with Shiryu. Doc Q could get another one into his Scythe, which would make him a 3 devil fruit User, combined with his Horse Stronger etc.
(And of course none of this has to happen, just fun speculating).