I've seen this and it's quite graceful to watch good players do it, kinda' like ballet. I think it would take a good bit of practice to get proficient at it. I saw Jeff Gillette the pro at Clint Eastwood's Tennis Club, Mission Ranch at Carmel doing it once, maybe it was with the Prof here. But you can't play with two rackets in competitive play, it's against the rules.
"...the human emotional system was not designed to endure the mental rigors of a tennis match." Dr. Allen Fox