The technology to antiquate BD already exists, it's only a matter of price point.
Price point and universality. Physical media make it easy to see the parameters of the market.. either you can support the physical format and can participate in its network effects, or you can't. Digital downloads are fractured amongst multiple DRM'ed silos (Apple, Microsoft, Netflix, Amazon, Tivo, Hulu, Sony, Comcast, AT&T, Time Warner, DirecTV, Vudu, Dish..), which reduce the value of each silo's players.
Network effects will decide how things go.
As for the 360 price cut I think it's pretty evident that they're going to make a move. The NPDs have to have been disappointing for Microsoft so far this year.