I remember dozens of people trying to convince me that Wally West wouldn't come back in Rebirth. "It's not going to happen, Nu Wally is officially Wally West. There's no place for the old character." And we all know what actually ended up happening. I don't buy for a second that it could never happen. It might not, but you can't prove that.
He said in an interview that he has big plans for Tim, and has also emphasized his tole in the series as the "emotional heart of the book". I guess that lends some credibility to the death theory, but that it will be temporary and lead to bigger things for the character. Like being essential to the Doctor Manhattan plot line.