I think the only significant reason to choose to change brands would be for video/fast liveview, the servo Af with video is pretty impressive to me, but you get the best out of it with STM lenses, and only the 10-18mm STM is going to be much use u/w. The D7100 has more pixels, better dynamic range, and you're already set lenswise.
As a now 48 hour veteran owner of the 7D2, I think for u/w alone it doesnt make much sense to change brands - if you did, the 70D would probaby cover most of the real advantages, ie servo AF video and liveview that can do fast AF, and its about half the price here for the body.
For abovewater for birds etc its great, but so far Im considering sticking with the 7D u/w even if the 2 does fit in my old housing.