I doubt the cover will show Blackbeard. At most, his only appearance will be chapter 440, and it climaxs right before the real fight begins. Save it for volume 46.
Also, I want to point out that
- Whitebeard and Redhair
- Blackbeard and Fire Fist
These two chapters gave us the most information on the greater powers of the Grand Line, and it tied a lot of things together. These two chapters are definitely OUT for the volume's name, because then, the focus of the volume would be drawn away from Luffy's family line, Usopp's return, Franky's and Thousand Sunny's arrival..etc.