okay, you have a few questions here:
1) If we could forecast that well, we would all be rich. however, historically prices in NYC real estate, including Brooklyn, have never gone down. That does not mean it can't happen someday, but to date, the trend is up, up, up - sure there are dips here and there, it is cyclical, but the long-run trend is never down.
2) the good time to buy is when YOU have found a property that fits your need and is in your budget. In the 1980's interest rates were upwards of 18%, people bought real estate then and have literally made millions, in a time when NYC real estate appeared doomed, and the country's economic system was in turmoil. Therefore, the good time is when YOU can afford to buy and when you have found something that fits your needs - if you buy to invest - it is ALWAYS a risk, Real Estate has never been a "short-term" investment. Buyers have been spoiled with the last few years of the real estate market, never before has real estate gained like it did the last 5-6 years. So understand that real estate does appreciate, generally it takes longer, a wise investment is never based on heresay - but on hard numbers.