Actually you can wait until the company have promotions. Make the camera looks to be more value-for-money. However, it usually only applies for entry-level cameras (e.g. Canon EOS 300D and the other P&S models) and don't usually apply to higher-end ones, and usually will take around 1-2 years after the model was first introduced.

The fact is that 2nd hand cameras are usually quite worth the dollar too, if you don't mind waiting for a good deal to come and having to deal with a lot of hassles.