Not one person who advocates for video calling on a cell phone has explained how it will work logistically. Just imagine trying to walk down a busy street and use the video calling function. You'd need to hold the phone at arm's length and keep it perfectly still to have a reasonable conversation.
Video calling makes zero sense on a mobile phone. It's fine for a home phone, where the phone can be stationary, but it's completely unfeasible in a mobile product. If (big, big IF) this ever happens, it will be a gimmick only.
Between the poor video quality such a device would entail and trying to sign one handed, I doubt it. Again, video calling on a mobile makes little sense.