Too early to tell for sure, but it doesn't just depend on weekly and yearly sales indeed, but also on how long they'll last. This could be used as an advantage, though, as using PC-like architecture and components, if Sony wants it will be able to cut price down to very low level, opening new markets and widening the target in the existing ones. But the ability to do it alone won't grant it, it will depend on the strategies for the next generation switch too, and not only Sony's ones, but also those of its competitors. An early start of next gen will almost surely lower this gen's potential, although if any competitor will decide a too early and half-assed start, the other two could resist with the current gen and totally crush its head start advantage launching their next gen consoles at their planned date, more mature and powerful and possibly more reliable too and at the same time less expensive to build.
This said 170M is very unlikely, while 110-130M should be a lot more reasonable target and 140-160M an unlikely but not impossible goal if almost everything will go right and the generation will last enough.







