Ars Magica Sixth Edition
There is no Ars Magica Sixth Edition, though Atlas has said there will "likely" be one in the future.
Atlas Games Announcement, 14 May 2015
Atlas Games posted a blog entry on 14 May 2015 about the future of Ars Magica. The parts relevant to a possible Sixth Edition are:
A Sixth Edition?
We have had many inquiries from both fans and potential designers about a new edition of Ars Magica. While we are likely to do a sixth edition at some point (emphasis added) in the future, we want to be clear that nothing we've announced here is that. We certainly have many ideas for what a new edition might look like, but such an undertaking won't be carried out lightly.
In the meantime, what we believe absolutely is that Ars Magica Fifth Edition is and continues to be a compelling, fun, mature product line with a deep backlist, excellent support, and a magnificent fan community. We think that it remains as viable for play now as it has been for the past twelve years. If you're a fan, we hope you'll continue to enjoy Ars Magica. If you've never given it a try, we hope you'll give it a go!
Posted by Cam Banks on 14 May 2015
Gen Con Seminar 2015
Andrew Gronosky (talk) 19:59, 4 November 2016 (MDT)
There was a panel discussion at Gen Con 2015 (on Saturday, Aug. 1, at 5:00 pm) about the future of Ars Magica. Andrew Gronosky and Erik Dahl were in attendance, as well as several Atlas Games people (John Nephew, Jeff Tidball, Cam Banks, and special guest Jonathan Tweet).
The executive summary of that meeting is that Atlas has no immediate plans to start writing a Sixth Edition of Ars Magica (as of August 2015). They are, however, quite interested in new games and products related to the Mythic Europe setting. Atlas indicated the Ars Magica / GUMSHOE crossover game Tales of the Quaesitors was in development, and representative of the sort of product they'd like to produce in the future.
There was an engaging discussion between Atlas and the fans. Fans indicated interest in supplements or perhaps spin-off RPGs set in variations of Mythic Europe, such as a Mythic China book or an Ars Magica "prequel" game set in Imperial Rome and centered on the Cult of Mercury. Atlas seemed to like hearing fans' suggestions and indicated more discussion with fans at conventions would be very welcome. You can use the "Ask Atlas" topic on the Atlas forums to inquire about their convention schedule. When it comes to ideas for what future spin-off products you might like to see, it's best to check in with the fan community to catch up on what has already been proposed or may be in the works.
Tales of the Quaesitors
Tales of the Quaesitors is not a new edition of Ars Magica. It's an Ars-Magica related product that probably counts as part of ArM5 because it's set in the ArM5 universe using different rules.
Tales of the Quaesitors is mentioned in the Futura Artis Magicae: The Future of Ars Magica blog post on the Atlas Games site as a standalone investigative RPG using the GUMSHOE system.