The latest "One Piece" Chapter 861 spoilers seem to indicate that Luffy and Bege will be able to successfully execute their plan of assassinating Big Mom even if her son Dogtooth is around. If they will be able to kill the Yonkou, does that mean Katakuri's Haki ability is not working anymore? Or could the plotters be able to distract him from using his prophetic powers?
Perhaps Dogtooth was already satisfied when he was able to foil the attempt of Jigra to kill his mom. Jigra is one of the guests in Sanji's and Pudding's wedding who wanted revenge for the killing of his father. Katakuri was able to sense what the organ trader will do and killed him before he can execute his plan. However, Jigra's plan is not connected with the plan of Luffy and Bege. Perhaps this is the reason why some spoilers say Dogtooth will drop his guard in "One Piece" Chapter 861.
Since Katakuri's Haki ability can only see a few seconds into the future before it happens, he could have assumed that the threat on his mother's life is over. He will probably go into a festive mood in "One Piece" Chapter 861 and will just enjoy the party. This could give Luffy and Bege the opportunity to execute their assassination plot against Big Mom.
That is why some "One Piece" Chapter 861 spoilers indicate that Dogtooth will not be able to foresee that Bege will use a KX Launcher to kill her mom. Therefore, there is a possibility that Luffy and Bege will be able to accomplish their mission. However, the two didn't know that Big Mom has some plans of her own.
This may complicate the situation because as some spoilers of "One Piece" Chapter 861 suggest, Big Mom is planning to massacre the Vinsmoke clan during the wedding. Her plan will start as soon as Pudding shoots Sanji. Admittedly, the whole wedding event will be thrown in disarray with two plans being executed by two different groups. Fans will know what will happen when this chapter is released on April 3, 2017.