I doubt it's likely to happen. Facebook has the API and the power. Not sure Facebook cares about tapping into iOS more than just an app does. They already have a huge install base on iOS devices at this time.
Facebook stinks as a software developer. (Right down to their own website.) The features are there, but the execution sucks.
It's not just the IOS apps that is bad, it's the Android and WP7 apps too. The camera and messaging apps being separate just attests to how awful the main app is (which already has these features built in and work POORLY).
Facebook is taking a LOT of heat on this, and more now they are traded publicly. FB wants this type of integration, but their challenge is finding a revenue stream, something they're not great at doing is making money. (Also a factor to why their stock is not meeting expectations, because now that they are public they have to discolose more fine details, and it's not a pretty picture.)
More FB traffic is via mobile (which is ad free) than their web site, where they have ads and things that generate income for them. Anything to keep people using and accessing Facebook is good for them. For them, that is more posts, more uploaded photos, and things you'll want to go back to a desktop version and see in larger scale later where they can sever you up ads.
In the past, FB tried to black ball Apple for payments citing using their API would tax their servers and cost them money, wanting Apple to pay them a fee. (Go back to the sad launch of Ping.) All FB really did was put a wall up to additional site traffic, and despite their user base, how many people really log in all the much? Their earnings tell a more realistic story about this.
So long winded as this is, it doesn't matter what their install base is on ANY platform. Their mobile apps such and perform poorly. Where they've grown in through integration into platforms and the web. (Like your FB login working anywhere, post to Facebook from news apps, etc.) They need people posting so people are viewing. Half the time I think of uploading a pic to FB, I say screw it because their app sucks and I don't want the irritation of using it and only load certain pictures. If I could 1 click from the photo app, I'd probably use the feature 100 times more. And so would a lot of other people.