ironkurtin has a point. Anything can change, and if we hesitate to buy based on our thinking we will be bigger or smaller or what-not 6 months from now then we are denying the bodies we have. I am a firm believer in the fact that we need to dress the bodies we have and appreciate them. Now a medical condition, pregnancy or ongoing weight loss/gain might make me postpone a larger purchase, but otherwise no. We've had some recent health scares with people very close to the family (one diagnosed with Type II diabetes and one tragically dying of an early heart attack), and it frightened me into a fitness routine. I've lost about 10 lb so far and intend to keep going for a while, so I am holding off on most purchases for now (except workout gear!).
But handbags and shoes are great investment pieces if a person is actively losing or gaining (thatis, if your shoe size doesn't tend to change)! And Jewelry!