You can't take anything we've seen as a measurement of how close they are to release. It's not a couple of guys in the office recording a few minutes of gampeplay and chucking it on youtube. Rockstar are a big, professional company. They had someone with lots of video experience, probably marketing background, directing the clip. Storyboards detailing the shots, transitions, progression of the mini-story in the trailer. Then taken the appropriate shots showing what they'd like the end-product to be like.
They're not going to put cars with broken textures or physics glitches in their videos. The trailers have shit all to do with what their product looks like in it's current stage. It's a preview of the end product of the game. Otherwise, trailers for any game wouldnt be released until weeks before the game's release.