I must say I was quite excited when I read the headline. After reading the actual article though I must say I am much less so.
It seems like this is an argument over who can stream what content from where, assuming that the streamed content was already legally obtained. In this regard, if Amazon and the RIAA DO battle in court, I feel like very little will change in the ways of RIAA's current copyright laws. Furthermore, I suspect that the RIAA knows its bounds, and will avoid going to court outright against Amazon especially since their argument seems to be rather weak. I think the best we can expect is an undisclosed settlement between the two.