As previously guessed, the Simpsons character fated to die in an upcoming Simpsons episode next season is almost certainly Krusty the Clown’s formerly-estranged father, Rabbi Hyman Krustofsky.
A recently-added copyright record for an episode entitled “Clown in the Dumps” simply confirms it:
Who’s the only clown we know of in the Simpsons universe? Krusty, of course (Sideshows Mel and Bob are mere assistant clowns, in my estimation). Why would Krusty be in the dumps? Because his father just died, that’s why. The clues are piling up, and they all point to a dead rabbi.
I would bet my remaining bitcoin on it!