In an interview of Rowling, she is questioned without revealing anything too important to the plot. A specific question asked during this interview, was about upcoming deaths. This is what leads me to believe that Dumbledore will not be alone much longer. This is a quote from Rowling herself, "I need to be more explicit: Dumbledore is definitely dead." So that pretty much blows your theory out of the water, however you did a good job thinking it through. What leads me to believe that Dumbledore will have company soon, quoted from Rowling states this when asked if she could, what characters would she have over for dinner: "Harry, Ron, and Hermione... [Rowling pauses; thinks about a different character who's dead but does not say his/her name. King interjects: "they could be dead"]. Dumbledore.... [another pause]. Hagrid."
That pause leaves me to believe that Hagrid may not be that "healty" in the next book. My opinions are based entirely on what I get from you guys, and sites concerning the controversy on the subject.
I suggest you read over the following pages for controversial takes on the subject:
Their Reasoning:
http://www.beyondhogwarts.com/harry-potter/articles/dumbledore-is-not-dead.htmlClues/Reasoning behind these ideas:
http://www.beyondhogwarts.com/harry-potter/articles/dumbledore-clues.htmlClues/Reasoning that It was setup between Snape and Dumbledore:
http://www.beyondhogwarts.com/harry-potter/articles/snape-clues.htmlPossible loopholes in the story:
http://www.beyondhogwarts.com/harry-potter/articles/unanswered-dumbledore-questions.htmlMore proof in such on the demise of Dumbledore:
http://www.beyondhogwarts.com/harry-potter/articles/new-revelations.htmlThere are plenty of ways you can research this , and even more concerning the interviews taken place with Rowling. I have no doubt that Dumbledore will appear in some way shape or form in the next book. Whether it be something he left behind, someone talk to him in a photo, or ( like harry had seen his parents ) as a ghost. You will never know until you read the next book I presume. But as I have previously stated, I have not and do not plan on reading any of it. I read 1-4 of the series a few years back, and haven't had the urge to pick it back up. But I did find it interesting that Dumbdore was pronounce dead, so I have done a little research to better examine a theory on it. However in all controversy, Deagol deserves well earned credit in his reasonable theory, but I now think Dumbledore is dead and will not physically return.