Replying to GH4 vs A7s

I currently have the 5d mark iii which I bought when I wanted to stay 50/50 between photos and video but now I want to concentrate on video. I will be filming action sports and promotional video to begin with but I don't want to be tied down to a specific area of film making. I have researched both the cameras in question and I have a few issues with both.

Do you think the rolling shutter issues of the A7s will rule it out for filming action sports? (philip bloom seemed to think so)
Do you think the weaker low light performance of the GH4 is a major draw back?
Will I have to sell up all my glass and move to nikon if I were to go with the GH4?

These are just a few questions but I would love general opinions as well. Also are there any other cameras that you would suggest on a similar price point.

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