I work in the electronics dept. of a large Sears store in central CA. New models start to arrive from late February thru mid May, with some high end stuff coming in even later. Initially new model prices are higher than equivalent previous year sets, come down a bit after a month or so and stay stable until the holiday season.
Unless there's a specific upcoming model with some compelling new feature not available on current sets you're better off financially getting an outgoing model.