The tech site BGR supposedly have confirmed that the above image, and the additional images in the link below, are of a new variant of the Samsung Galaxy SII that is AT&T's version. This new variant obviously has a slide-out keyboard, which is a surprising thing to see, considering one of the selling points of the device was that it was so thin and light. Here's a quote from the BGR article,
Live images of the device reveal the Galaxy S II model number, SGH-I927, along with additional details surrounding the sleek Gingerbread phone.
It seems odd to me that the AT&T version would be so much different that the original version, but I suppose stranger things have happened. There was no indication of pricing or availability yet, and I suppose we will just have to play "wait and see" to determine the veracity of this info. Take a look at the additional pics and let us know in this thread what you think.

Here is a link to the rest of the pics: Additional AT&T SGH-I927 Samsung Galaxy SII with Slider Pics

Source: BGR