Could the US Navy's DDG(X) grow into a very large destroyer before construction?
Short answerYes. Its projected displacement had already risen repeatedly as more equipment was added, and further growth was likely.
NotesDDG(X) could approach the large displacement proposed in the question. Its estimated weight had already increased more than once before construction began. Each added capability places another demand on the hull. Further growth was therefore more likely than a stable early figure.