Well honestly this argument is just like the permawhite debate. Because so many people claimed forever it would ruin the character, it was a betrayal to everything, and they could not do it and it would fail. Then the film came out and people seemed to not say a thing about it because they realized in the context it worked.
Just like how some are not open to the idea with the evidence given above that there is a possibility that Batman may die. Since Nolan, Bale said it is a definitive ending, WB has already said they have to reboot the Bat franchise afterwards and the teaser sure gave hints to it.
To me the permawhite debate (as most remember I was always in there saying it does not ruin the character and it will still work and it did) is just like this one. Those claiming he can't die to me is almost parallel to the Joker being permawhite, some made a deal of it where it was required and the core aspect of the character, it was not.
So a death is possible, more were in denial before the film came out of him being permawhite. This mirrors it almost exactly.
Now am I saying he will die? No. Not at all, but I'm open to the idea that he will, mainly because there is a greater chance then ever before that he may. Not saying a greater chance, but a greater chance then ever before.
So I keep an open mind because in the end it is all about context, and execution (as it was with a non-permawhite Joker). And as before I just have faith the team knows what will be best for "their" story. However there has been some great discussion in here just like the permawhite debate, and the people I've been debating have been very civil and fun, so this I have a feeling will be the permawhite discussion all over again. But in reality I think we will have some of the most intelligent and interesting discussions in here, on both sides of the argument.