If I had to pick what is the "hottest" issue in professional responsibility today, I would say it is a collection of issues all related to the notion of unauthorized practice of law, and the "threat" of competition from non lawyers in the provision of legal services. This includes issues related to DIY legal services, such as those provides by LegalZoom and others, the regulation of non lawyers to provide legal services, artificial intelligence, and so on. It is no accident that the ABA recently created a commission on the future of the practice of law to study these types of questions.
This is why a recently published comment in the NY Legal Ethics Reporter is so relevant. It is called Virtually Unclear: Will Legal Tech Companies Bridge Justice Gap or Fall into UPL Abyss? and you can read it here.