What? The question about should I buy a computer now? People ask that because everyone has a different situation. In some situations people have a computer which died, and they need it to get work done. In that case, buying a new one is a must. Or in other cases, when the new generation is a year away, people should not wait in most situations. But around now, when you have a perfectly good 2012 MBA and Haswell is 5 months away, waiting is a good choice.
Again, why ask the question then? Each of the cases you pointed out are clear cut, based on your own diagnosis.
1. Computer dead? Buy a new one.
2. Computer outdated, but close to refresh and can wait? Wait.
3. Computer outdated, but refresh is far out and can't wait? Buy a new one.
At the end of the day, the question can be reduced to: "Am I in a position to wait or do I need to buy one right now?"
I will be jumped on shortly with comments like: "This is a forum! People can ask questions!" and "Everyone's situation is different!"
The answer to both is, of course. But a few moments of thought would lead a person to their answer.