Apple has never made a dual sim iPhone and the chances of that happening are bleak. But according to 9to5Mac, the iOS 12 developer beta 5 version had an interesting field in the diagnostic report. There was a reference that indicated at the presence of a second sim tray.
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The diagnostic report references “secondSimStatus” hinting at the possibility of a dual sim slot. But unlike other dual sim phones which house a single tray for two sims, the next iPhone might sport two trays. This inference can be made thanks to another line in the diagnostic report, “secondSimTrayStatus”. Another component refers to a “dual sim device”. If Apple is indeed trying to implement a dual sim design, it beats me why they would use two trays. Maybe there’s trouble getting a longer sim tray in one slot?
Dual sim devices are particularly popular in India and other Asian and European countries. A dual sim iPhone will allow users to change carriers without the need to carry a separate phone or swap out sim cards. The use of dual sim is rare in countries like United States, Canada and Australia. So Apple might choose to release this phone only in select markets.