I believe he will fight Sakazuki.
First off Oda decided that the two chief news Luffy and we as the audience should know about are
> Sakazuki's victory over Kuzan
> Teach's rise to being a Yonko
I mean he even drew them in the exact same manner
Let's even compare the reactions Luffy has to both of them.
> Luffy sitting and listening to a story about Sakazuki and at the mention of Sakazuki's name his scar starts throbbing in pain and he starts sweating showing visible anxiety at the mere mention of Sakazuki
> Whereas, when it comes to Teach, Luffy doesn't care and is spacing out and focusing on other things, such as eating
And the reactions make perfect sense. One Piece is a story and one in particular in which "ambition", "determination", "drive", "willpower" or whatever other synonyms one prefers directly confers martial prowess. This concept is so prevalent that it is physically instantiated in the phenomenon known as haki:
And who was the one that made Luffy doubt himself? Who was the one that broke that indomitable will, spirit, or whatever you prefer?
It was Sakazuki of course. When he killed his brother in front of his eyes
> Sakazuki broke that spirit. Sakazuki made Luffy doubt himself. Out of countless ruthless enemies, it was Sakazuki, and Sakazuki alone that achieved that.
> Coupled with the symbolism in One Piece that scars represent, Sakazuki and Luffy are destined to meet and fight.