Yes, you receive Sport Rocketry when you renew your membership.
Your renewal may have happened 'between' issues. The Jan/Feb 2010 issue of Sport Rocktry was to have shipped on January 4th. If you paid extra for first class postage/shipping, you will receive it in the next 7-10 days. If you did not pay for the additional shipping, you can expect the magazine in 2-3 weeks.
Also, you can contact NAR HQ and ask about your subscription.