Vita was good tech for its time, but Sony basically just missed the boat for really super powerful mobile processors.
The Vita actually basically got the same chip the top of the line iPad had for 2011 even before the iPad 3 came out. With a freaking expensive OLED screen. For only $250.
The difference today though is the top of the line iPad processor, the Apple A9X *blows* the Vita chip out of the water. It's 500-600 GFLOPS vs. 30-50 GFLOPS (Power VR SGX543MP4+).
If Sony released a Vita 2 this year, absolutely they could have had a unified platform with the PS4, the tech just wasn't ready for prime time (or even close) 5 years ago. It is today. The tech is here.
Nintendo has a wonderful oppurtunity here to use some seriously incredible tech (and affordable) if AMD can give someting comparable to what the other mobile vendors are doing. The thing is these super powerful mobile chips ... they're having trouble finding applications for them ... a phone, even a tablet only needs so much power, but a mobile game console could easily use all that horsepower. PowerVR is trying to impliment the GT7900 processor (their top of the line 800 GFLOP GPU) into cheap Android mini-consoles for example.
Nvidia's Tegra X1, you can buy that in a $199 console for almost a year already with 3GB of RAM. And that's with a large mark up on the hardware. These are not expensive processors, because that's the nature of the mobile processor market ... all vendors are asking for more powerful chips (for yearly refreshes) but at a cheap cost in exchange for high volume orders. This is a great situation for Nintendo to get themselves a really fantastic chip.
Which is probably what Nintendo saw coming, I'm sure they sat down with AMD 3-4 years ago and they mapped out where mobile chips would be at today and from that they started to seriously think about a unified platform I think.
