I think 100m-115m is probable. The PS4 does not have the early support of Japan like the PS2 did, nor the price value (I doubt the PS4 goes under $200 like the PS2 did eventually) so I doubt it comes near that number. Also this generations is probably going to be a year or two shorter than last.
You're Gonna Carry That Weight.
Xbox One - PS4 - Wii U - PC