No, Graham is right on definition. NG-PON is understood to be a generational scale-up (4x for ITU, 10x for IEEE) in capacity, regardless of whether it is achieved in the time domain or the wavelength domain or both. In terms of ITU standardization, it would be better to speak of 5th Generation PON (S-PON, A-PON, B-PON, and G-PON being 1st through 4th generation, respectively).
10 Gbps PON or X-GPON is a natural evolution of the technology. My understanding of NG-PON is a new technology such as WDM-PON. Am I wrong?