Read about it here:
In short. Onecare will be discontinued in June 2009 for sale at least. By then, I would expect that Morro will be available in Beta. So, if you did not pay for Onecare, you won't need to for Morro either.
I cannot say how good this may be because it is likely Microsoft will strip off the additional functions such as tuneup, photo sharing, backup etc. So, it may be a give and take thing.
The only advice I can give for those who are facing expiry of their subscription soon: Renew of switch to a new Anti Malware first. Morro will be a while. If your expiry is far, go on with it and wait. By Spring 2009, I will expect a beta of Morro to be available.