Nope Brook vs Who's Who is not happening, even if Jinbe does fight Jack that doesn't mean Brook is going to fight Who's Who. Also Who's Who even if he is kind of nerfed is still more stronger than Brook, Brook is strong but I don't think he is strong enough to handle Who's Who by himself.
Also Brook helping Robin fight Black Maria makes more sense than Brook fighting Who's Who, Black Maria has a yokai theme to her and Brook is a talking skeleton.
I still have my doubts that Jinbe vs Jack will even happen, if Oda wanted Jinbe to fight Jack or Brook to fight Who's Who then he would have already setup those matches already.
I can’t wrap my head around Inu beating Jack honestly. It’s wrong on so many levels.
1. Kinemon is the most relevant Scabbard plot-wise, yet Oda didn’t even care enough about him enough to make the fight anything more than a one shot. Why would the less relevant Inu get an entire chapter or two of him fighting and beating Jack?
2. Neko has just as much of a grudge as Inu does against Jack, and the two are a pair. Why leave Neko out if Oda intends for Inu to win somehow? The reason seems rather obvious to me. Oda DOESN’T plan on letting Inu win, so he left Neko out because he knows that Jack couldn’t beat the two Dukes combined
3. Inu was shown as being, at best, equal to Base Jack. How does Inu beat Hybrid Jack, nevermind a potential Awakened Jack?
4. Why would Inu get to accomplish so much more than his fellow Scabbards? Ashura got taken out by a Kanjuro drawing to save the others. Kiku got stabbed by Kanjuro. Kinemon got to beat Kanjuro, but Kanjuro isn’t nearly as strong as Jack, and then Kin got taken out by Kaido. Raizo is gonna beat Fuku, but Fuku isn’t particularly relevant. Neko is, at best, beating Perospero, but I doubt that will happen. Izo and Kawa are unknown, though odds are they will only help out a little against King and Queen before jobbing. Denjiro is unknown, but it’s not like he’s gonna be taking out any Calamities. Inu beating a Calamity would be odd when the rest aren’t being nearly as important.
5. Jack being the only core BP not taken out by a SH would be out of place