Apple has confirmed, through an unlikely update, that iOS 12.1 will indeed have Group FaceTime and Dual-SIM support for compatible iPhone models. The confirmation came with an update to the official iOS 12 User Guide in Apple Books. The update outlines what is new in iOS 12.1 with these two features the first two mentioned in the guide.
Both Group FaceTime and Dual-SIM support have been a part of the iOS 12.1 beta testing cycle and it was widely expected that they would make it to the general release of the update this year. But, in normal Apple fashion, the Cupertino company would only say that the features were beta features. This update to the Users Guide pretty much solves the mystery.
With the release of the User Guide update to iOS 12.1, it also very likely means that the general release of the update is not far away. That could be as soon as this coming Tuesday at the Apple Event in New York. That event is expected to see a new generation of iPad Pro tablets that support Face ID, something that is in the iOS 12.1 code.
If you have not downloaded the iOS User Guide from Apple Books, you can do so here. It is a free download and it can be handy at times to have when you are trying to find a feature or setting on your iPhone or iPad.