The release will mark more than a full year since the third collected volume, no doubt due to the current bi-monthly schedule of Saikyō Jump where Naho Ooishi’s “chibi” spin-off manga is serialized.
The fourth volume will pick up with the Uranai Baba arc in Dragon Ball SD chapter 29. If the previous volumes and their roughly ten chapters’ worth of standard material are any indication, the volume should take us well into the 22nd Tenka’ichi Budōkai. The volume is available for pre-order at Amazon Japan.
The January 2016 issue of Saikyō Jump, released earlier this month (04 December 2015), contained the spin-off manga’s 40th chapter since its 2011/2012 reboot.