The evidence strongly suggests that this is a virus which mutates, and is continuing to mutate today. Just a couple of days ago, they were stating that SARS is here to stay and that we needed to learn to deal with it. Personally, I don't know how they can say that if the thing keeps mutating.
Sure, it's possible that the virus will mutate into something even more deadly, but it might mutate back into something that doesn't affect us at all, like it was before.