Telephony Online reports that Alcatel-Lucent is leaning towards a hybrid WDM-PON approach as the next gen alternative to the current GPON FTTH networks:

In a hybrid system, carriers would replace their GPON wavelengths with four different GPON wavelengths, all within the existing 20 nanometer window but partitioned in smaller 5-nm slices. Carriers might add filters to the nodes between their central offices and their customers rather than to all customers’ homes.