Or will the 5DIV be 45 MP
That's one possibility, that the 5D Mk IV is going to be the big MP camera, and eventually a future 6D Mk II will gain a better AF and more FPS...
I'm not sure what you are basing that on. This could very well be the 1D Xs.
Speculation. It's fun. Sure, it could be called 1D Xs. But again, I don't think so, especially if it's going to be a non-integrated grip body, which is my preferred option. In the other case, why not? But unlikely. Remember Canon introduced the "X" to represent the merging (crossing) of the 1D and 1Ds lines, and now what? Splitting in two the 1 series again and keeping the X, though both FF?