For sure the number of 'clickers' will never reach 0 but this is definitely a trend worth monitoring.
Also there are so many types of advertising... Banner advertising is but one. Things go out of fashion, other types of advertising become popular, etc
I monitor my ad revenue and ROI very closely, and have done over the last 10 years. Slightly more than some random unscientific 'study' ;)
For sure the number of 'clickers' will never reach 0 but this is definitely a trend worth monitoring.