You really think PS4 is going to sell less than PS3? Come on. PS4 is ridiculously ahead of PS3 launches aligned. In US alone it's going to sell far more than PS3 did. Also WiiU and Vita both have probably passed already that 10 million mark. Somewhere around 15 million is more likely for both.
Well it's a toss up whether PS4 sales will overall eclipse PS3 sales.
It depends on how soon Sony are willing to take a hit on profits by reducing the price, seeing as I could see them keeping it where it's at for a little while longer. Bundle deals will be the order of the day I think.
Also I feel like the majority of sales so far have come from the hardcore/casually interested in video game buyers. The super casual folks need to dive in as well for sales north of 90m+.