I hope that if it uses auto-complete and predictive text voice that it doesn't cause problems people make sure to video the results.
That's one of the things that will be very interesting. My German has gotten rusty in my old age because I just don't have the opportunity to speak it a lot, so I sometimes forget certain words and how to spell others. When writing my relatives in Germany, I generally have Google Translate open so I can check on the occasional word or phrase.
More often than not, the translated phrase from English to German is an incorrect usage or incorrect syntax. Sometimes even nonsensical. Because I still know German, I generally catch it right away, and actually, it usually reminds me of what the correct phrase is. However, that's writing, where you have the ability to check/correct things. That won't work in near real time communication, so it will be interesting to see how bugs are worked out in that regard.
Google Translate has been around a good long while now, and it still doesn't get it right a good portion of the time. It usually does well enough so people can make themselves understood for basic conversation, but it certainly doesn't allow for say, a deep philosophical conversation on the works of Nietzsche or whatever.