There are still no solid specs for the 5D IV, so I am undecided about the 1DX II.
If the 5D IV has 24 MP, a good framing rate, and high ISO IQ is reasonable, I'd be more inclined not to get a 1DX II and just continue with the 1DX for the rare occasions.
OTOH if the 5D IV has ~30 MP and greater...