The primary design goal of (r)evolutionary NG-PON1&2 was the provisioning of an ever increasing capacity to cope with video-dominated traffic and handle the explosion of mobile data traffic by means of offloading. Recently, however, questions on the future of “post NG-PON2” have surfaced whether to shift its research focus to business and operation related aspects and move access technology into a substantially different direction than continued capacity upgrades. In fact, recent studies indicate that ultimately the major factor limiting the performance of 4G mobile networks is latency rather than capacity of the backhaul. In this paper, we review recently proposed low-latency techniques for NG-PONs that require architectural modifications at the remote node or distribution fiber level and highlight advanced network coding and real-time polling based low-latency techniques that can be implemented in software, enable NG-PONs to carry higher traffic loads and thereby extend their lifetime, and maintain the passive nature of existent optical distribution networks. Furthermore, we elaborate on emerging trends and open challenges for future post NG-PON2 research. To better understand their true potential, we put them into a wider non-technical and historical perspective leading up to a sustainable Third Industrial Revolution (TIR) economy and its underlying Energy Internet.