From a Tynion interview:
"
How would you describe the situation Tim Drake’s in? It’s ingenious, because he’s effectively dead in the universe of the book, but we know he’s out there and coming back, which circumvents the typical anticlimactic superhero death-and-resurrection cycle.
The best way to describe it is having my cake and eating it too. We didn’t want to do the standard fake-out, okay the character’s dead and then three issues later reveal he’s alive. We wanted to show people right away that this isn’t something we did to shock readers, this is all part of a story.
We wanted to make it clear that everything that’s happening with Tim is because
we think he’s one of the most important characters in the DC Universe,
not an expendable character that we’re going to toss on the fire to make all the characters cry. Now, at the same time, we get to use him to make all the characters cry.
One of the things that’s interesting about Tim being the one taken off the board is that he’s such a bright character. From what we’ve seen of Rebirth so far, it looks like it might be a referendum on dark, post-Watchmen superhero stories vs. a more optimistic ideal, of which Tim is kind of an avatar.
All I’d say is what Mr. Oz says to Tim Drake when Tim is pulled into the side world. All I can really do is point to the text at this point, and then say: This is all a bigger story. The fact that it is Tim, and Tim is central to all of this, that is relevant and important. You’ll be slowly discovering why over the next few months or years. Tim’s a character who I feel like in the New 52 got brought over to the Titans side of the universe, and was sort of taken away from Gotham. Being able to root him as a crucial Gotham figure before sending him off into maybe the biggest story Tim has ever been a part of in DC comics history, that’s something that is important to me and makes me happy that we were able to do."