If 'blockable-by-IR' technology made it into the iPhone camera, it'd be a week before an IR filter exactly as you describe emerged as a Kickstarter project.
It would probably be titled 'Decensored' and accompanied by a spoof of the famous 1984 Super Bowl ad. Or, failing that, a guy in a shed with some IR filters, a pair of scissors, some Pritt Stick, and a dream.
If I were Apple I would make the IR processing happen at hardware level (so no jailbreak) and I would make sure the hardware would stop working unless a physiological level of background IR light is picked up.
That means that an IR filter physically placed in front of the objective would stop the secret signal but make the camera useless as well.
Besides which, when Apple adds features, they traditionally do so to benefit their users. I'd suggest that, even though they cite concert censorship as an example of use in the patent, that's probably a cover-all-bases addition; we're more likely to see an iPhone IR sensor that enhances the user experience rather than one that impedes it.
It would probably be titled 'Decensored' and accompanied by a spoof of the famous 1984 Super Bowl ad. Or, failing that, a guy in a shed with some IR filters, a pair of scissors, some Pritt Stick, and a dream.