The engineering of systems involves many different stake-holders, each with their own domain of expertise. Hence more and more organizations are developing an ever grow-ing number of Domain Specific Languages (DSLs) to allow domain experts to express solutions directly in terms of rel-evant domain concepts. This new trend raises new chal-lenges about designing not just one DSL but many of them, 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 ad-dressing them. We detail one of these challenges, which is the safe reuse of model transformations. Indeed both DSL definition and tooling (eg. checkers, document or code gen-erators, model transformations) require significant develop-ment 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 tool-ing across several DSLs, even when these DSLs are concep-tually 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.