Did some more digging and DTV made the announcement at the DTV Revolution Conference, in 2016 - ie "the sunset of three key SD satellites".
There is a lot of speculation on what this means as there are multiple satellites with different capabilities that can be moved or new satellites launched.
But the consistent thought is that SD transmission (ie MPEG2 transmission) will end. SD programming would still be available on HD channels. The result is that SD receivers will no longer work and apparently this applies to 101 SD programming starting in 2019.