He will return to Hachinosu with Law captured and we will get some info on the Rocky Port incident, them Garp will sacrifice himself against the BBP to give SWORD the opportunity to escape.
Like its obvious that Garp plot is the basic trope of "Old Mentor sacrificing to save the New Generation", and the only character that could kill Garp is Teach, as this would make both, Luffy and Koby, held a grudge against him
The ship going to Egghead probably have Kuzan, Devon and Laffite.