It was only inevitable, now that the company has come to its senses "Whatsapp" and Apple's "Messages" might hit hard, can't say in terms of sales for respective brand's devices though.

I believe zeuS already had p2p capabilities as is evident from the last source leak. A well setup botnet even if based on p2p would eventually require a middle-man-server to coordinate its actions among the nodes in foreign networks especially if they are behind NAT.