I went back in the portal, and it did not respawn. I do not know if there is a way to get him to spawn again though. It would seem lame if you can only kill him once especially for those who spent weeks+ on a map lol.
EDIT: I ended up quitting w/o saving, just so i can fight him with friends. It seems you can replay him over and over, but you cant progress your save if you kill him. Lame-o. Was hoping they'd allow it for xbox.
Major problem for me though, is he NEVER stopped to do that ender acid thing, nor did he ram towards me. With this i used many arrows attempting to kill him, once i ran out i started to sprint towards him, unfortunately looking at endermen the whole time so im being overwhelmed while the dragon just sits around.
Next try it worked, easy as making a redstone door.