I was very sad to hear of the impending demise of OneCare. I am quite a fan of it and have licensed it on all of my own machines and those of my family. It is unobtrusive, unlike so many of the alternatives and has the quality of 'it just works'. I can only assume that it hasn't made enough money. Microsoft are dressing the decision up as "Improving Global Access to Core PC Protection" but I can't see that offering "Morro" requires the cessation of OneCare. Occam's Razor therefore indicates a financial motive. It isn't going to die immediately, but subscriptions will be cease to be available from June 30th 2009.
P.S. It seems that a 'morro' is "a rocky outcrop in the shallow waters of a harbour, often round in shape and sometimes very high". It is also the name of the harbour fortress of Havana, Cuba.