According to the Generalist Badge Implemented blog post,
there must be at least 200 questions in all 40 of the top tags before this badge is awarded to anyone.
Right now, our "tag no. 40" (margins) features exactly 200 questions. IIRC, the tag has hit the limit yesterday, sometime in the afternoon. I had expected that the first Generalist badges would be awarded either immediately or in the morning of the next day (today). But no user has been awarded a Generalist badge so far. When can we expect our shiny new badges?
(Just in case anyone asks: I guess there should be at least a dozen "instant awards". I'm no. 5 rep-wise at the moment, and have a total score of >=15 in 31 of the top 40 tags.)