He died in Infinate Crisis # 6. He destroyed Alex Luthors machine and died in the process. He saved the Universe. But....he may come back. You'll find out whenever you read TT #34 what I mean by that.
Bart's been missing scince IC #4, right? The Issue where Superboy Prime killed all those Titans. He and the other Speedsters tried to Trap SBP in the Speed force. He disapeared along with the Speed Force shortly after. Where is he now? WHo knows. Probally find out in future issues of TT or Flash which will be relaunced in the Summer. (He could very well be the new Flash. Who knows.)
It's possible. Though, I don't believe so. Flash and his family got pulled to "Somewhere Else" before the other Speedsters were able to drag SBP into the Speed Force. Bart went along with the Speedsters. I think he got absorbed into the Speed Force, and wherever the Speed Force went after that, is likely where Bart is as well. THough theres no telling where Wally is.
They're basically trying to get the team back together and they are about to team up with the new Doom Patrol of which Beast Boy is now a member, to take on the new Brotherhood of evil. They are also trying to get Wonder Girl to rejoin, but she's still bitter over Conner's death and Robin's seeming abandonment of the team and her after the Crisis to run around the world with Batman and Nightwing for a year.