Worth quoting. It is not guess work. That have some data that indicates a clear trend. The trend is to attack non-Microsoft items that have not been updated by the user.
When a Microsoft Windows machine gets infected by viruses/malware it does so mainly because users forget to update the Java JRE, Adobe Reader/Acrobat and Adobe Flash. This is revealed by a survey conducted by CSIS Security Group A/S.
So there you have it. Little to do with the OS. Much ado of users who have not been educated.
Anybody reading this, please look at the link given by BC above. It is based on collected data, not pipe dreams. It is not the OS at this point in time. Maybe it was always the user.