From what ive heard of the Colombian military- i think they could take Chavez quite handily. Such a important war so close to our borders, i find it difficult we would abandon a major friend in the region. If im not mistaken, Brazil dislikes Venezuela as well, and they are the major power down in South America from what Ive seen.
Chavez is a crazy dictator- but i dont think he would go through with it, hes been slowly losing support at home and the last time he tried this he had to back down due to disfavor.