Is this the "upcoming Colonial Marines supplement" people were talking about back in October, or is there also an actual USCMC source book on the way later on?
And if this IS that -- will this book in that case just be that single one-shot cinematic three-nighter adventure, or will it significantly broaden the info on the Marines provided in the core book for use as campaign background also outside DoW?
Nope. There is an upcoming Colonial Marine Campaign book coming up after this one.
edit: Andrew E. Gaska (setting writer) wrote on FB: "Our plan is to do at least one cinematic scenario and one campaign sourcebook per year."