For an anime centered on pirates, One Piece's lack of a character with an eyepatch is a strange omission—however, there's hope that one will appear before the anime ends. One Piece is an adaptation of Eiichiro Oda's manga of the same name. Oda claims that One Piece will end in the next few years after both the manga and the show have been ongoing for over 20 years. Even when the One Piece manga and anime end, Netflix's upcoming live-action adaptation gives hope that the world will not run out of One Piece content any time soon.
One Piece touches upon classic pirate iconography with many of its characters. Crocodile has a huge golden hook on one of his hands, and Red Leg Zeff has a wooden peg leg after one of his legs was severed when trying to rescue Sanji. There's also an abundance of Jolly Rogers, scraggy beards, and pirate hats. Even Rob Lucci's pet pigeon, Hattori, plays upon the cliché of pirates owning parrots. This makes the lack of any character wearing an eyepatch glaring, which is intentional from One Piece's mangaka Eiichiro Oda.
Back in 2007, Oda stated that towards the end of One Piece, there will be a pirate that appears with an eyepatch. The reason that the anime has not featured an eyepatch so far is that this long-awaited moment will be rendered more impactful. This mystery leads to several theories about who will be the eyepatch-wearer, and the most credible theories surround Luffy and Blackbeard. The possibility of a completely new character being the eyepatch-wearer cannot also be ruled out. Especially since in 2007's One Piece Paradise, Oda stated that he's "itching to draw" the character with an eyepatch. This could imply that Oda is so excited to draw the character because it's someone that is yet to be introduced and could have a large impact on One Piece's endgame.
In Oda's early concept art for One Piece's Blackbeard, there's a drawing of him with an eyepatch. While this does not confirm that Blackbeard will be the eventual eyepatch-wearer, it does lend credibility to the theory. In One Piece Paradise, Oda explains that he understands the association between the classical appearances of pirates and eyepatches. Blackbeard is arguably the character in One Piece that is representative of modern interpretations of pirate appearances, and his appearance also shares heavily resemblances to the real-life Blackbeard, named Edward Teach. If Oda wants the eyepatch to be symbolic of the old interpretations of piracy to fully come into life in One Piece, then Blackbeard would be a prime candidate.
In One Piece Paradise, however, Oda also explains that One Piece is the story of how a "normal looking boy" becomes a pirate. One Piece sets up that Luffy will eventually fulfill his dream of becoming the Pirate King, and wearing an eyepatch in the anime's finale would be emblematic of this, as it's the last piece of pirate iconography to appear on the show. Luffy losing an eye and wearing an eyepatch would also mirror Luffy's backstory. As a child, Luffy stabs himself in the face to try and join Shank's pirate crew. Luffy's face scar is another mystery that took years until it was revealed. Since Luffy first scarred himself to try and become a pirate, it would be fitting that he could make a larger, similar sacrifice to solidify his claim to be the Pirate King, having to wear an eyepatch in the process. It may be a while until an eyepatch appears in One Piece, but as with many things in the anime, it'll be well worth the wait.