According to sources such as 5thGenRams and the YouTube video posted by a Ram Dealer in Arizona, it will be a part of a new package. The Technology Group (ADG) will include: 1) Heads-Up Display; 2) LED Center High-Mount Stop Lamp (3rd Brake Light) with Camera(s); and 3) Rear View Digital Display Mirror.
That being said, it could be that Ram will offer some of these as stand-alone options... well the only really stand-alone option would be the Heads-Up Display since the Digital Rear View Mirror would need the new 3rd Brake Light to function as intended. In the YouTube video, there was no mention of any of these being offered as stand alone options and the Technology Group would only be offered on the Laramie, Laramie Longhorn, and Limited (they tried to build a Big Horn with it and couldn't).
There's still a lot to learn with the 2021's so we'll just have to hang tight until everything is officially announced (which will hopefully be soon). It sounds like these new options/packages were just pushed out to the dealers late last week, so I'm sure they're still figuring out what options/package can and can't be ordered on the different trim levels.