TLDR at bottom*
To say it outright, Kaido is practically unbeatable. That is assuming he will be defeated by the end of Wano Kuni arc, though. At the very least, I don't think Luffy can beat him, and I don't think Luffy will acquire Gear 5/awakening yet. It just feels too early, since he was barely even able to defeat Katakuri with the newly acquired snake man.
It is well known that Blackbeard is heavily referenced around the number 3. This is an excerpt from Erkan12's theory titled What are these 3 Ancient Weapons? to highlight what I mean:
"When you think about it, Teach has a very weird interest in 3, and it's really interesting, taking 3 skulls on his jolly flag, giving 3 eye scars, using 3 pistols, and using 3 beard buckles..."
As well as that there are three types of devil fruit: Zoan, Paramecia, and Logia. It's no secret that Blackbeard is searching for all of the strongest devil fruits he can find. So, the logical conclusion is that he will end up with 3 powers: one zoan, one paramecia, and one logia. It's already been stated by Blackbeard that he believes the Yami Yami no mi, a logia, is among the strongest devil fruits, and the Gura Gura no mi is generally known as the fruit power that could destroy the world and by proxy, assumedly the strongest paramecia.
So if Blackbeard already has the strongest logia and paramecia, then that just leaves out zoan. And I believe there is no better way to get the strongest zoan than to take it from the man known as the "Strongest Creature", Kaido. Since so many other characters (like Big Mom) seem to have their eyes set on Wano, I don't find Blackbeard going as well too hard to believe.
I suspect he would show up to kill Kaido near the end of the arc similarly to how he killed Whitebeard at Marineford (all factions fighting each other as he swoops in amidst the confusion). He would then take his devil fruit power and have all three. It's hard for me to say how he will take the power or kill Kaido, but I suspect the Yami Yami no mi has something to do with either.
TLDR: Blackbeard will show up at Wano near the end of the arc while everyone is distracted fighting each other, and will somehow kill Kaido (or just take his fruit power), thus gaining the three strongest devil fruits in the world.