The current designs are close to a year old now and apple updates infrequently and generally does not cut the price. So you are paying a premium for buying a one year old design. Imho the best moment to buy is early in the product cycle. You maximise the period the design is fresh and reasonably current. I bought my 15" mbp last October when it was just out.

The flipside is of course that recent models are rather disappointing in many ways. It's only marginally faster than the 2012 model it replaced, contains the same amount of memory and cpu cores. And there is the keyboard, which is a severe downgrade and has many flaws and the well documented reliability issues. That 2012 model was the best piece of hw I ever owned. So, you can wait but don't expect any miracles.