They will add the missing nationals (BravoHD+,TNT-HD, HDNET/Movies) when they feel they can absorb the costs and bandwidth requirements. Since Comcast doesn't have a separately priced HD tier (only $5 for the HD STB and another $5 for the DVR if you want it) they can't just add a few channels and hike HD tier costs by a buck or two to pay for it. Plus, they have many old systems that are bandwidth-challenged right now, so if they added another national channel those folks will start/continue screaming. Plus they are trying to establish VOD and dual-tuner DVRs to better compete with satellite.
It took a year and a half to add DiscoveryHD. While there are many "in-the-know" folks on this forum about Comcast, no new rumors have been circulated in the past few months. Sometimes someone says to be optimistic, but that's all.
Before DiscoveryHD was added, there were swirls of rumors alive for months. Nothing like that now. So I would thiink that optimism is fine for the long-term but not for the next few months.
What is great is that D* is launching more satellites to support HD. When it can show local HD and gets all the available national HD channels (will INHD1&2 stay only on cable?) then Comcast may feel it is in their self-interest to expand their HD offerings. A year from now I probably won't watch anything in SD except Jeopardy.
Rich N.