The change that is coming in February 2009, is from analog signals to digital signals, not to HDTV (while HD *is* digital, not all digital is HD). The change will affect only over-the-air transmissions, not satellite TV or cable.
Your Winegard antenna is capable of receiving digital signals, so you do not have to change that. The only change you will need to make to view over-the-air programming with your Winegard batwing antenna, is to either get a TV with a digital tuner (if you don't already have one), or get a converter. If you need a converter, the government will provide you with up to two $40 coupons to purchase them.
Here's a website that will explain it all, and give you a place to order the coupons should you need them.