I heard that once you complete the story you dont get to play anymore?
Same as Fallout 3, until broken steel..

Is this true?

Yep, been confirmed for months.

It's not the end of the world either.

My world is over

Yes once the game ends and the ending cutscene shows then the game is officially over and you cannot play anymore until you load a previous save or restart.

just save before your last quest, beat game, reload, have funn terrorizing the wasteland untill expansion comes out. i know thats what im doing and i look forward to it.

It end when ya beat the game. On the other hand, beat game, and ya get a ending that depend on the action of what ya did in the Mojave. In theory, this should encourage ya to play the game again to see the other side of the game.