Well, we know next to nothing about the PS4, but trends from other systems released in the past few years would suggest that the PS4 will have a painful birth and first year at least, then if Sony gets its game together, it should pick up from there.
So I don't see the PS4 regularly doing over 100k a week within a few months of its launch. With the 3DS selling north of 150k, I think it'll be a couple years yet. In the long run, it's a possibility, but far from a certainty.
In the long run, it's safe to say the 3DS will end up around the 100 million mark. But will the PS4 get there? Unlikely. 70-80mil is most probable, but again it depends on what the system has going for it.