I am sure it could do it, but why would they cut into sales of the soundbridge? Think about it, why sell a product that does video and audio when they already sell a separate product that does internet audio? It would be cool, but I don't see them cutting into sales of one of their own products. They did name the product the Digital Video Player so I am guessing that they are going to focus on video streaming with it.
My basic and first question is to nail down first if it could be done.
As to the business viability, there are plenty of reasons that Roku could and should consider doing this. They include that one cannot listen to radio and watch tv at the same time (generally) so if one is ok with using one's tv speakers for radio, it could be an interesting new "channel" on the roku to have access to audio channels.
Roku over the last year or two has at times seemed lukewarm in its focus on the Soundbridge, so I don't know where they're going with that.
Anyway, I still need to verify for-certain that the Digital Video Player could perform some or all of the functions of the Soundbridge.