Prophecy2k
Veteran
Programming to the metal is pretty much irrelevent when the graphics output from iPhone6 will most likely be indistinguishable from the NGP...and since NGP uses the same architecture as iPhone porting instead of down to the metal coding is more likely.
I think you may be assuming that the iPhone 6 HW will even see games developed with the same quality of assets and content on iPhone 6 as on NGP. There's a fundamental point to be made that not very many devs will be keen to bust $'s on hi fidelity game assets that push the iOS HW when margin on the games sold is so low, especially on a market so saturated (by the time the iPhone 6 releases it'll be even worse).
I mean look now, we have what, 2-3 games on iPhone 4 & iPad that even use the full capability on the HW. NGP and 3DS are a different story because the sale price per game can support the investment in hi quality art assets for those games.
Edit:
If anything we'll see more ports of NGP games ported to iOS than the other way around (when talking about the top end games). The majority of stuff on iPhone 6 will be the same stuff we're seeing on iOS now with low budget cartoony graphics games that aren't even close to testing the HW.