the Sony FE mount f4 version is pretty similar to Canon's current offering(based on a visual comparison alone.)Yesterday was the day I made the move. I bought the a7 and will soon sell all my DSLR gear. I cannot imagine a reason to go back to DSLR's as long as the weight is nearly double an a7 sized camera and the size is much larger
How much would a 70-200 lens for the a7 weigh and how much smaller would it be?
That being said, if you read my whole comment you would see that I specifically mention that most pros will still use DSLR's. However, I know about 10-15 people with DSLR's(all amateurs) and only 1 of them has the 70-200(the f4 he bought for 350 bucks on CL) or anything longer(besides those cheap 18-300 superzooms.)
I myself want a small camera with a few small primes for when I travel for extended periods of time and for carrying around daily in my backpack.
If I have to sacrifice ergonomics with long lenses, that I never use, for this, then that is an easy choice to make.
I know for people who regularly use long, heavy lenses this sentiment may be very different, but that is not the majority of DSLR buyers.