For some reason this was never mentioned in any of the demos, and since it's a huge thing, unfortunately I'm thinking the answer is no. 
Can Sprint's WiMax and the HTC Evo allow you to be on a voice call and surf the web at the same time like AT&T + iPhone?

Can Sprint's WiMax and the HTC Evo allow you to be on a voice call and surf the web at the same time like AT&T + iPhone?