No, I do not think Ganondorf is a descendant of Demise. As already mentioned, his dialogue points at an "incarnation of his hatred", which could be taken several ways depending on how you look at it. I find it interesting how Wolf Sage considered him a representation of the world's end in a previous post in this thread, that really makes Demise sound like an interesting character to me because him being the looming threat you hear about through the whole game (and possibly the whole series, if you allow me to extend it to that) makes him more than just a character in my mind.
My interpetation of his curse: based on his dialogue at the end, I don't think it points at any direct re-appearances by him anytime soon. That doesn't mean that his looming threat persona I mentioned can't have some sort of hand throughout the rest of the series. Maybe I'm taking it too far if I say that Demise fuels the motives behing the actions of the other villains in the series, but I'm certain that while Demise isn't the full reason Ganondorf looked for the Triforce, I think he was probably what took him away from any possible redemption. Ganondorf already had several motives of his own, as Wind Waker's pre-final battle cutscene revealed (I'll put it here just in case):
Ganondorf said:
My country lay within a vast desert.
When the sun rose into the sky, a burning wind punished my lands, searing the world. And when the moon climbed into the dark of night, a frigid gale pierced our homes.
No matter when it came, the wind carried the same thing... Death.
But the winds that blew across the green fields of Hyrule brought something other than suffering and ruin.
I coveted that wind, I suppose.
I say that Demise's hatred wasn't the driving force, but combined with those already present factors I get that he was probably the catalyst that finally made Ganondorf go on his power crazy rampages and made his motives all the more significative in his own eyes.