Amazon is giving out free HotS keys with preorder:
http://www.amazon.com/StarCraft-II-Heart-Swarm-Pc/dp/B002I0KP4G/ref=sr_1_2?s=videogames&ie=UTF8&qid=1353724780&sr=1-2
The beta code was given out instantly.
If you're unsure on the price after that, I believe you have the option to cancel it. I personally kept mine as I know I'll be getting HoTS.