Definitely sill relevant. While your right that the philosophy behind behaviorism has largely faded, behaviorist research methods are still quite dominant.
And even though someone like BF Skinner wouldn't find a wide audience on a "Cognitive Sciences" site, behaviorist accounts of phenomena still generally have the advantage of parsimony (i.e. Occam's Razor), so it would be wise to have any current behaviorist theories in plain sight and not dismiss them out of hand.
Behaviorism is a subset of psychology and psychology as a whole was merged into the Cognitive Sciences proposal.