It's also unknown what exactly will get covered in a second season, but it will no doubt lead to the Arabasta Arc.
Koby & Helmeppo's Future in Netflix's One Piece
On top of the post-credits tease, the finale of Netflix's One Piece also has Vincent Regan's Garp taking Morgan Davies' Koby and Aidan Scott's Helmeppo under his wing and how his training "[has] been called the worst kind of punishment."
But will that mean a continued appearance for all three of them in Season 2?
One of the biggest changes in Netflix's One Piece was focusing more on Koby and Helmeppo and having them pursue Luffy throughout the East Blue under Vice Admiral Garp.
In the original manga, once Koby joined the Marines in Shells Town in "Chapter 7," readers didn't see him (or Helmeppo) in the main story again for another 425 chapters, sporting a completely new design (right) in his next appearance.
However, for readers who paid attention to one set of cover stories, a series of supplemental material told through the cover pages of certain chapters, "Diary of Koby-Meppo," showed some of Koby and Helmeppo's training by Garp at Marineford.
Will Koby Appear in Season 2 of One Piece on Netflix?
Unless Season 2 cuts back to Koby and Helmeppo's training at Marineford under Garp like the cover story or anime, then live-action fans won't see these two for quite some time. At a minimum, the next time they'll be seen is in a hypothetical third or fourth season.
As it stands, Smoker and Tashigi will replace Garp, Koby, and Helmeppo as they continue the pursuit of the Straw Hats into the Grand Line.
However, cutting back to them even once or twice in a follow-up season could be beneficial in the long run for the show; it could help establish the status quo of the Marines in the One Piece world while also including or even mentioning important Marine figures who will appear later in the series in bigger roles.
Season 1 of One Piece is currently streaming on Netflix.