The engineering of systems involves many different stakeholders, each with their own domain of expertise. Hence more and more organizations are adopting Domain Specific Languages (DSLs) to allow domain experts to express solutions directly in terms of relevant domain concepts. This new trend raises new challenges about designing DSLs, evolving a set of DSLs and coordinating the use of multiple DSLs. In this talk we explore various dimensions of these challenges, and outline a possible research roadmap for addressing them. We detail one of these challenges, which is the safe reuse of model transformations. Indeed both DSL definition and tooling (e.g., checkers, document or code generators, model transformations) require significant development efforts, for a limited audience (by definition), because the current state of the art of Model Driven Engineering still makes it hard to reuse and evolve these definitions and tooling across several DSLs, even when these DSLs are conceptually very close to one other. We outline a new extension to the Kermeta language that leverages Family Polymorphism to allow model polymorphism, inheritance among DSLs, as well as evolution and interoperability of DSLs.