To attract significantly more people to the 360 (as opposed to the Wii or PS3) Halo: reach needs to be something more special than a Halo game with better graphics. I'm not convinced adding Natal to the mix will necessarily do it, unless you can only get Natal by buying a new 360, which I seriously doubt will happen.
As a software seller I think the popularity of ODST indicates that Halo: Reach will sell a lot of software.
Halo: Reach released with a new (slim?) sku would push a decent amount of hardware. A Halo skinned 360 would sell very well too, though it would be a limited release so would not necessarily translate into sustained increase in HW sales.
Ace in the hole? By itself no, not in terms of 360's overall sales performance. As part of a package yes.
“The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.” - Bertrand Russell
"When the power of love overcomes the love of power, the world will know peace."
Jimi Hendrix
