A thoughtful response- and the answer depends on whether the First Law of Thermodynamics holds- or not. If the universe is 4-D you are positively correct...either crunch or heat death.

Personally, I think a 4-D universe is preposterous, but most scientists believe that's the way it is. Of course, cosmic truth is not decided by a democratic election, not so far as the universe is concerned anyway. Whew!

Regards, Sam Cox