Slightly overblown - Comcast will not kill AppleTV or Roku, they are already being killed by smart TVs/players ;p
Netflix is already accessible to many people WITHOUT AppleTV or Roku:
any "smart" TV or Bluray player (meaning ANY modern Samsung, LG... TV or player) already have not only Netflix, but Hulu, HBOgo etc ...
While not everyone has those TVs/players (needs 2010+ models usually), in few yeare everyone will have.
But Comcast seems to be first or among first cable operators not afraid to include streaming apps on their box. Samsung/LG and other TV/player producers never had competition issues with Netflix, but cable providers sure do - most cable providers in world also offer their own video-on-demand options, and allowing Netflix directly compete with those (if not with cable core bussiness).
So cudos to Comcast for allowing Netflix in any case ;p