As much as I love Case Closed, we've already received official word that they're not going to do any more of the series. Here's a post on the funimation site that says as much: http://www.funimation.com/case-closed/forum/funimation-shows/and-more/case-closed/the-status-of-case-closed-updated-4212011#comment-72441
Key quotes:
"We're not going to buy anymore of the series. It just didn't sell well enough, unfortunately. There's no way we (Acquisitions) could ever convince Gen (our CEO) to get more. I absolutely adore the show, but I couldn't in good conscience ever recommend buying more. we always have to put the good of the company before our personal preferences in anime."
"Thank you very much for supporting the show, but I'd give up on ever getting to buy more at least from us. :/"
So no. No more series. There's no way they could justify it. It's a drama that's tough to market to American audiences and is over 500 episodes long -- that's way too risky. They've already put way more money into the series than they probably should have (even though it's very appreciated).
The only thing we could possibly hope for are the rest of the movies/specials (ie Conan vs Lupin III), but even then..
"We're still open to getting more movies, but nothing is in the works."
Nothing is in the works. Which breaks my heart, but there you go. I have vain hope that they'll release sub-only box sets in the future like they did with Super Gals, but I'm not holding my breath.