This is a list of SMGs that will appear in the multiplayer for Black Ops 2. Note that this information is legitimate and that it came from those who actually played the game at Gamescom:
It's official. The MP7 will be returning. This was one of the most powerful SMGs in MW3. In Black Ops 2, it seems as if this gun has an even faster rate of fire than before. This is a German submachine gun that was developed by Heckler & Koch. It has been produced since 2001 and according to it's Wiki page, it's basically designed to work like a scaled-down AR.
This one was first shown in the single player campaign mode footage back in June/July. The Chicom CQB is an automatic bullpup SMG that boasts 40 rounds per magazine. It's important to note that the Chicom doesn't actually exist in real life (remember, all of this is set in the future). Here's a screenshot of it being used from a first person view:
The PDW-57 appeared in the multiplayer reveal trailer. During the trailer, you could see that the player was using some sort of special scope that allowed him to see enemy figures through surfaces. So far, I've been unable to find any information on real-life variants. In-game, this gun can hold 50 rounds per magazine, which is pretty healthy, to be honest (although the rate of fire is high on this weapon, so it might not make much of a difference):
Skorpion EVO 3
The Skorpion EVO 3 was developed in the Czech Republic. In real life, it's magazine capacity can hold up to 20 or 30 rounds. Its usage began in Slovakia back in 2002. Other variants of this weapon have appeared in COD games over the years. For example, in the previous game, there was a Skorpian machine pistol.
The MSMC was shown during gameplay clips of the multiplayer. This is a real life weapon that is called "The Modern Sub Machine Carbine". Developed in India, it can fire off 700 rounds per minute. This particular SMG was designed in a way that allowed it be fired with only one hand (like the Uzi). It has a magazine capacity of about 30 rounds. Here's a screenshot of the gun in question: