If the Shinigami can die (Rem, the dude before, some Shinigamis mentioned by Ryuuk), then hey can also be born, right ? I mean, over time, the population lowers, even if only 1 or 2 shinigamis die every century. It is also said that shinigami cannot have sex, therefore they must somehow also appear. And Shinigamis all have slighlty human traits, and I believe that's what they use to be.
I firmly believe that Light has become a Shinigami. Ryuuk said that what would await Light would be neither Hell nor heaven. As for the last panel of 107, the author was not necessarily referring to Light, just humans in general. And Ryuuk is not the sort of "person" to disclose a lot of information.
Or maybe I'm just delusional because I didn't want the series to end like this. But I really think Light is now a Shinigami.