@Roo decided to recheck this.
The last comment made by editors in Nov 2019, and even they say OP won't finish in 5 years (lol)
https://worstgen.alwaysdata.net/forum/threads/former-editor-naito-changed-his-mind-regarding-“5-years”-issue.1707/
But Oda's SBS in vol 97 (Sept 2020) calls into question if Oda means Luffy's journey and not serialization. However, it heavily depends on translation. Eten and other translators took it as this:
Even Greg clarified that it "might" mean this, but also could not:
Among others who believe he meant the whole thing or not the whole thing. Give Greg's little thread a read, it's interesting