I want to know if a particular date (for instance, October 1, 2010) is a good date to go ahead and buy a Macbook pro, or whether I should wait few months for new models to come out. How can I figure out whether a computer I buy will soon become obsolete?
MacBook Pros aren't going to be updated until at least January, if you can wait 3 or 4 months, I suggest you do so.
However, if you need it before the end of the year, go for it. I doubt we'll see any major advancements anyway. You'll only miss out on slight speed bumps not a quantum computer.
See the comments to improve the question, but Macrumors' buyers' guide always has suggestions if now is a good time to buy.