How much proof do I want? Well, I think a definitive, clear answer one way or another from, say, a dev who is working on the game would be sufficient. And, it just so happens, we have that already!

Gradius1:

We have no plans to use Natal for F3 so please stop making threads about it :-)

Thread here

Look, I would have absolutely no problem with using Natal in Fable III in an optional capacity, but this was one of the first things discussed about this game, and we've been told that there are currently no plans to use it. Gradius said it once before, in clear English, that there are NO PLANS to use Natal. Until we get a solid and clear confirmation otherwise (read: not speculation), we should take this statement as confirmation of there being NO PLANS for Natal at this stage of the game.

Also, there are at least 3 other threads about Natal on the front page of these forums (one of which was actually created by you). There's really no need to start another one to discuss the same thing.

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Futurama is back, baby. Complete with the original cast!