I've done some investigating.
The "CS:GO Teaser" is actually a fake teaser. What Dex posted is the legitimate, and original teaser for Counter Strike Online.
Counter Strike Online was released in 2008 and was geared towards Asia's market.
If you look at the youtube account that released this fake CS:GO trailer, you'll notice that it's very shifty. It has one video, and is a normal user account.
This user has edited the teaser for CS:O, and has fooled thousands/led thousands to believe it's the legitimate trailer. Lol.
Although Valve has confirmed CS:GO. They have not released a trailer themselves. I mean.. C'MON people, when has Valve ever released a video a year away from any of their game's release dates (remember that you also have to factor in Valve time)?