Way I see it, the 1DX is already a better camera than 5DSR in every way except resolution. The A7R II however has all the cool stuff which Canon lacks.
If planning to use Canon lenses it is worth checking out if they work satisfactory with the Metabones IV with latest firmware before buying however. I only have the old version 3 with old firmware which works good with some lenses but won't lock focus with others. When it locks it is more accurate than with my Canon bodies however. Version IV is said to be much better.
Using native lenses is best, then the autofocus of the A7R II is in some ways even better than Canon's (eye focus, face recognition, subject tracking).
I think would be wise to try the A7R II for a while before buying if possible, long enough to get familiar with it because it may take some time to configure and get used to before you can use it at full efficiency.