EDIT: VOLUME 54 COVER IS OUT.
Well with volume 53 ending at chapter 522 and with the manga being up to chapter 533 right now, it seems we have enough chapters for volume 54. So let's just start with the speculations.
Title: "No One Can Stop this Now"
Covor-Characters: In the front Luffy running with Buggy, Gardino and Bentham following him. In the background Magellan sitting on his chair with Magellan and Sadi-Chan next to him. Hancock and Momonga stand somewhere on the side. And in the far background face close ups of troubled Ace and Jinbei.
Color: Grey
Chapters: 523 - 531
Of course we all know that I will be 100% wrong.^^