As Ryco poster earlier, there's a rumor that the next, or one of the next, DLC options for Mass Effect 2 will be a new squadmate. Well, while finishing up some loose ends on Ilium in-game today, I stumbled upon further proof that, at the very least, this character exists.
There are two passageways that separate the three main areas of Ilium. When walking through those passageways, a woman usually reads news over the speaker system. While my Shepherd was taking a stroll through one of those passageways today, I caught the tail end of one of her reports. Apparently, one of the big corporations in the Entarus Systems had some kind of omni-gel tech stolen from them and they were "blaming the theft on a human calling herself Kasumi."
This in-game info, bundled with the leaked roster containing her name and the concept art, is enough to confirm her existence, and allow one to properly assume that she will be another recruit for Shepherd's team. Alas, Bioware has still not made an official announcement, so only time will reveal the truth.