At some point full frame cameras will come down in price & as Nikon only has one type of mount, unlike some (Im looking at you cannon), I dont want to rebuy lenses.
Eh, I think DX cameras and lenses will be around for quite some time. The smaller sensors will always be cheaper, and there's a major benefit to a smaller and lighter camera.
That said, if you suspect that you'd be swapping up to Full Frame in the future, even if it's five years from now, then it's a good idea to try to maintain a collection of FF lenses. There's always the option of shooting in DX mode, but I could see how some people would cringe at the thought of not using all their pixels.
Nikon only has one type of mount, unlike some (Im looking at you cannon)
Does Canon maintain multiple mounts? I know they completely switched mounts in the late '80s for autofocus lenses, but I thought their previous mount was just plain discontinued.