I love my Canon system, but the whole darned thing becomes so heavy and cumbersome. Have to carry separate batteries for the 7D2 and for the 1DX2, separate chargers, separate cards and readers (cannot read the c-fast card on regular readers). Considering you have to take the lithium batteries in carry-on baggage, I have half a bag full of just batteries between the two Canon bodies and my two Sony's (A7R2 and Rx1R2). This will be a huge weight (and probably cost) saving for me.
The only thing is I am not sure if the Sony 100-400 is going to be as good as the Canon 100-400MkII which is superb. Given that the 24-70GM is so sharp (I found it sharper than my Batis 25), I expect it to be.