Indeed, that's why Nikon's current strategy has some elegance to it- you build a D3 body line and make D3 and D3x's there- same body- no new line necessary. You build a 24MP sensor line and you make D3x and D700x sensors there- Same with D3/D700 sensors and components. Basically you end up with twice as many camera models with the same number of parts and you can run the component parts at full production and slap them in whichever body is selling the best at the moment giving you the ability to be relatively nimble in sales/stock terms.
I think this is one of the things people miss when they start to talk about things like the D700x "cannibalizing" D3x sales- the difference to Nikon is just scheduling which pentaprisms and bodies get made at what ratios- and volumes make up for margins enough that it's just not such a big deal to them, they're running the same lines and making/buying the same parts.