My theory is:
Franky vs Senor Pink should be a one chapter conclusion (Franky winning)
Robin, Bartolomeo, & Cavendish vs Gladius should be one chapter (Robin's group winning)
Zoro vs Pica should be 2 chapters (Zoro winning)
Kyros & Rebecca (if you count her) vs Diamante should be one chapter (Kyros winning)
Luffy vs Bellamy should be at least 5 panels (Luffy winning)
Luffy vs Doflamingo should be 4-5 chapters (Luffy winning)
So this arc should be over around 780 of January-February 2015
Franky vs Senor Pink should be a one chapter conclusion (Franky winning)
Robin, Bartolomeo, & Cavendish vs Gladius should be one chapter (Robin's group winning)
Zoro vs Pica should be 2 chapters (Zoro winning)
Kyros & Rebecca (if you count her) vs Diamante should be one chapter (Kyros winning)
Luffy vs Bellamy should be at least 5 panels (Luffy winning)
Luffy vs Doflamingo should be 4-5 chapters (Luffy winning)
So this arc should be over around 780 of January-February 2015