Deadline doesn’t have any plot details (saying only that this is “a series version of one of the most praised movies of all time”) so we’ll have to speculate about whether this will still be a prequel story, as Pileggi mentioned over a year ago:
Of course, you can’t pick up from Goodfellas, since we murdered everybody, or rather, everybody was murdered! There’s nobody left. But I think we’re going to figure out a way to do the early years – sort of a prequel. The part of the movie people often like best is the opening third, where all the funny stuff is happening, and there’s so much we could fit in.
Of course, as we’ve talked about before, Goodfellas was the product of Pileggi working with the actors and Martin Scorsese, and there was a lot created on set by Scorsese and the actors. So while Pileggi is certainly the author of Goodfellas as a story, he isn’t even close to being the author of the film. That just means that this TV series will probably be like the film in name and concept only, but I guess you knew that.