In a surprise to, well, pretty much no one, Yun and Yang have confirmed to be in Super Street Fighter 4 Arcade Edition. A location test is currently underway, and beyond the confirmation of the two new characters, there are also reports of gameplay changes. According to a post on SRK, Yun's Super is Genei-Jin and both him and Yang have their target combos from Third Strike. Hakan has also allegedly received some buffs, with him now being able to "stack oil" and even combo into oil off of a standing light kick.
Oichi over at Versus City is also reporting than Zangief's EX Green Hand does not knock down. Also, arguably more surprising is that blocked Blanka Balls now recover half the distance that they used to, which will make it much easier for many characters to punish, not just Balrog and a few others. He also mentions that Juri's Fireballs now "combo naturally" though I'm not entirely sure what that means. Seth's Jumping Fierce Punch has also apparently been nerfed, but it's not clear by how much at this point.
Keep in mind that this is a location test, so none of these changes are final or 100% confirmed. We'll continue to post more information about this revised version of Super Street Fighter 4 as it comes through!
More reports are coming in via Twitter that day one Genei Jin combos for Yun are doing roughly 50% damage to the opponents life bar.
Yang also has an EX Teleport though its properties are unknown at this time. Probably invincibility of some sort!