Correct, currently Webroot is predicting a large influx of ad/spyware to begin targeting Firefox over the course of the next year.
Of course there was a similiar article stating the same thing earlier this year. But I tend to agree with them on this. As Firefox's market share has grown they become more and more a target for this type of exploit.
Additionally, the next several weeks could provide Firefox, Opera, and other browsers with a large increase of useage (dependent upon the Microsoft/Claria rumors), making them much more appetizing targets.
Here's to the future...