I assume the two sensors are not at all too different, except that Nikon doesn't make the D3X chip, Sony does.
Outourcing chip fabrication is normal. In fact having two source protects you against e.g. a fire in one fab.
It's an A900 chip with Nikon electronic wizardry.
Pure speculation on your part. We know that Sony had SOME input in the design. That's all we know.
It's a great camera for sure, but it ain't all Nikon, and that's for sure too.
You think Canon design and manufacture everything in their camera? They don't.
Sony even assembled the chip it. It's a Nisony.
That's not bad, but that means Nikon is limited to what Sony can and is willing to do in the future with their FF Sensors.
Pure speculation on your part.
What makes you think that Nikon haven't had key input to the design of the chip? After all, the D3 chip is 'pure' Nikon. People assume that Sony have Nikon by the nadgers. But it could be more of a symbiosis, Nikon chip design expertise, Sony fabrication and electronics expertise. Pure speculation on my part. But just as (un)likely as yours.
That's the problem with the inter-porn-net-web. It's full of people making statements with 100% certainty but which cannot be substantiated. Remember the Nikon MX camera that was a dead cert? Even the PC-E lenses were used as evidence by the experts.