I think most of the input comes from dealers, who are the ones that place the actual orders for new RVs. Their marketing people surely get ideas from all over, but the ones that get listened to the most are the ones backed with the $$ that place orders.
Dealers order what they think they can sell, so they are listening at least a little to their customers. Things like how long, how many beds, price (for sure!), and so on.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL