I think that Hasselblad felt that they needed to go big or go home. Hence, the mirrorless MF design, as they probably felt that they had very little to loose. Making the change to the lens mount essentially freed-ed up their overall design space, but you can only do this infrequently.
Having Sony and Fuji consider MF, would certainly ramp up the potential demand / volume of the sensors. However, there is essentially a price floor on the sensors due to their size and the number that can be laid out on a wafer - and wafers as the basic raw material are expensive. Probably the best that can be done is to scale the wafer size so as to optimize / maximize the number of sensors that a single wafer can produce. That will essentially lock in the best cost possible for MF sensors to whatever specific sensor size - right now the 44 x 33.
Sony has the lion's share of the sensor market. They are also trying to put the overall company back together, and the profit margins from the sensors is one of their bright points. I doubt that they feel the need to reduce margins to ramp up sales of sensors, so that everyone else can sell cheaper MF bodies. There is a minimum cost that will define the floor to the MF body market.