Incomplete-tantei wrote:He's known for being a troll.
Yeah, just think of how many of his answers end with, "(laughs)".
But he does have the ending planned out—he said that ten years ago. It's just he's added elements that he thought would expand the story, before he ended it.
(note, the below comments are not chronological)
(note2, Kochikame started in 1976 and has 198 volumes currently, with over 1800 chapters)
"(Have you already decided the end of Detective Conan?) Yes, I have. However, I don’t know when I’ll be able to draw it (laughs)." (Masters of Manga Interview)
"(Q: Does Gosho Aoyama already know, how the series is going to end?) A: He does already know what the last scene is going to be, but of course he won't reveal it yet." (Erlangen, Germany Interview 2006)
"(Q: How many more years do you set as your goal?) Gosho: Because I’ve been drawing it for 10 years, I haven’t thought of the future. Although I have already thought of the ending, because I can’t lay the clues if I don’t have the ending." (Anime 10 year Anniversary Interview 2)
"(Q: Does Gosho Aoyama plan to write the last volume already and to keep it in a safe for now?) A: No, he does not plan to." (Erlangen, Germany Interview 2006)
"(I'm excited to see it! When do you think you can write the last episode that you said you decided the contents of?) I don't know. But I don't think I'll exceed KochiKame in volume number (laughs). I've already decided the lines. The ending will be a happy one. This is my work, after all." (Otona Fami Interview 3)
"(Q55: When will the final confrontation against the Organization take place? Conan will win, right!?) A: Keep reading the manga!" (SDB40+)