Never. Look at Counter Strike, still kicking as one of the strongest FPS franchises with the same formula. Hardcore crowds might start preferring it again over CoD due to custom maps, though the sheer numbers will probably be in CoD's favour (although I wouldn't say by much, at least on PCs, CS is still immensely popular as it's very low-rent)
You don't really need much for a good online FPS. It needs to feel right and the maps need to be designed right. Once you've got a formula for both (actually the second is rather 'common knowledge', the first is the challenge and CoD's definitely gotten it very right), it's hard to go wrong. There's not much room for innovation either, not as far as marketability goes.
The only thing you're discussing when you mention CoD is number of copies sold. I don't mean this as an offense to the FPS crowd at all, but innovation is NOT something that's primary to them, polish is (same holds for MMOs to a large extent atm, though MMOs have far more room for improvement and innovation) and the eye candy doesn't hurt either. And it's not that they are "stupid FPS players", it's just that when you're talking competitive FPS, it comes down to the same old formula Counter Strike came up with more than a decade ago - make it fast paced, stick two teams against each other, use a few different modes, give a variety of weapons and make it all as balanced as possible.
So don't look to CoD to change or innovative competition to take over cause it won't happen. If you want a different kind of game, play what suits you. Personally, I like the Battlefield formula, big maps and vehicles add a lot of fun for me. I'd also be open to more dynamic and innovative FPSs, perhaps an MMOFPS/COFPS where players could team up and take challenges on together - something like Borderlands or Left 4 Dead, but a bit larger in scale and more akin to Battlefield ie. with a bunch of vehicles, large maps, perhaps some sort of fortifications, the end goal being dynamic cooperation between the players.
