Threat modeling involves the systematic identification and analysis of cybersecurity threats in the context of a specific system. This paper starts from an assessment of its current state of practice, based on interactions with threat modeling professionals. We argue that threat modeling is still at a low level of maturity, and identify the main criteria for successful adoption of a threat modeling approach in practice. Furthermore, we identify a set of key research challenges for aligning threat modeling research to industry practice, thereby raising the technology-readiness levels of the ensuing solutions, approaches, and tools.