For home consoles, I'm thinking 7th gen will end up at around 285 million or so and I think the 8th gen will struggle to get past 180 million.
Something like:
PS4: 85-90 million
One: 60-65 million
Wii U: 22-25 million
Handhelds probably about:
3DS: 80-85 million
Vita: 20 million
Basically, I'm expecting the handheld and home consoles combined to sell about the same amount as the home consoles did alone in the 7th gen. If anyone wonders why; take a look at some of my posts in the UNITY thread, I have written fairly extensive posts on it in there (hint; I think this will be a short generation).