I have been looking for the same thing, but for the older Mac Mini 2011, which appears to have a similar interface.
[http://d3nevzfk7ii3be.cloudfront.net/igi/AtfsmuBLiREVTEvA|Mac Mini 2011 wifi card]
[http://d3nevzfk7ii3be.cloudfront.net/igi/hstYSnNkuXWpf3Kf|Mac Mini 2012 wifi card]
Currently there is no ''replacement'' for the internal WiFi card, but [http://www.xlr8yourmac.com/feedback/802.11ac_Mac_adapters.html|there are alternatives].
I would hope that Apple doesn't change the Mac Mini style and releases a new Mac Mini with WiFi ac support in a similar minicard style as the 2011/2012 models, so I can order a spare part to replace the existing one.
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[http://www.quickertek.com/products/Ucard.html|QuickerTek] used to make a WiFi ac product called uCard which was an internal replacement for the AirPort card within the Mac Mini, however it was discontinued before I had even heard of it. :(
I have been looking for the same thing, but for the older Mac Mini 2011, which appears to have a similar interface.
[http://d3nevzfk7ii3be.cloudfront.net/igi/AtfsmuBLiREVTEvA|Mac Mini 2011 wifi card]
[http://d3nevzfk7ii3be.cloudfront.net/igi/hstYSnNkuXWpf3Kf|Mac Mini 2012 wifi card]
Currently there is no ''replacement'' for the internal WiFi card, but [http://www.xlr8yourmac.com/feedback/802.11ac_Mac_adapters.html|there are alternatives].
I would hope that Apple doesn't change the Mac Mini style and releases a new Mac Mini with WiFi ac support in a similar minicard style as the 2011/2012 models, so I can order a spare part to replace the existing one.