The developers have a tried and tested formula for their product that works for them, and continues to give people like us one of the best WWI aviation experiences around.
I doubt they will change that formula, (unless they want to go out of business).
New content in the form of BH&H is very much welcomed and we all wait the release with much anticipation.
As to it's 'classification' whether new game or add on dlc is pretty immaterial. If we want new content, it's down to the individual whether or not they will buy it of course, but if WoFF goes to the wall, I fear we will never see the likes of this type of genre ever again.
Anyway , all being good it will be available in around 14 days!