Since the beginning of the twenty-first century, headquarters and C2 systems of systems have largely evolved in occidental armies, enacting larger distances on the battlefield and increased heterogeneity of units. This evolution combines two related aspects that concern system of systems (SoS) engineering: organizational changes and digitalization. The use of robots and drones, as well as forthcoming next-generation weapon systems will lead to step up this evolution. In this paper, we adopt the model-based engineering perspective to review this foreseeable evolution, in order to identify open challenges.