Sure, there's a potential of gain, but I'm not convinced that this is guaranteed or likely yet. My problem with it from a business perspective is I'm not convinced that having the Neo out there is going to accelerate growth faster than if it didn't exist and they simply dropped the price of the PS4.
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Other factors is loosing gamers from the PSN ecosystem if you dont offer a high end product.
Lets face it, $ 200 AMD cards with 970 to 980 performance is the hot topic, an explosion of price vs performance.
If Sony do nothing which is what you are advocating, SOME gamers will move on to an ecosystem with more power (Scorpio or PC). And those gamers who want more are likely those who dispose allot of income to gaming.
I am one of those gamers, If Neo does not bump performance enough I will move in 2017 with so many good options coming.
Also if I do get a couple of Neo's, I will probably sell my ps4's on ebay, bring in some budget conscious gamers where £ 300 is too much for OG ps4. Neo sales could increase Ps4 ownership if consumers upgrade and sell their existing consoles cheaply on ebay - its not a zero sum game here..
Sony cannot afford to stand still when everything is going to change around them - Nx, Scorpio, 480, 1070 and Zen they are all coming in 2017 or this year.....
Remember 360 lost allot of gamers to Ps4, the might go back if Sony sit on their laurels, most of these were early adopters and high attach ratio consumers according to Sony I recall.