Since last summer, they have added the Discovery Channels, History, Big Ten, NHL, NBA, TBS. So I wouldn't say they stopped adding channels.
They just haven't added SciFi.
Discovery and History are the last adds I am referring to in the summer. Yes, they added TBS after being basically shamed into adding it by baseball fans in October. Big Ten is not national and hardly counts. It is a regional network available in states with those schools. They may have launched for everybody but said it would soon be available only in those states where the schools are. As for NBA and NHL, those are both season passes, not something that everybody gets. So really, the only true HD nationals they have added since summer are TBS HD and NHL Network HD. So pretty much yeah, they have not been adding channels.
Having 8 NHL Center Ice channels that air 1 game on 2-7 of the stations per day at the most for two and a half hours hardly counts as 8 different HD nationals. It looks like they are including that in the count though, which is very deceptive and you know it.