I'm no expert (I just started the Macintosh asylum because no-one else had stepped up to the plate), but my answer would have to be no.

My understanding of the matter goes something like this: The relative "immunity" of Macs has really just been a matter of small market share. Since winboxes have always been far more numerous, hackers are much more motivated to go after the Microsoft OSes. Thus, the main reason there are so few Mac-hungry viruses out there is simply because no-one bothered to create them. However, as Macs grow in popularity and gain more market share, hackers will be more inclined to seek our their vulnerabilities and try to exploit them.