unless you are frequently run and gun in poorly lit venues with a no flash allowed policy in place, you would be just fine with 24-70 / 2.8 glass.
if you can afford to take a breather while you are changing your glass, you would be even better served with a pair of nice and bright primes in your bag: say, 35/.1.4 + 85/1.4
please note: 28-70/2.0 is not a spectacular lens wide open at the wide end. far from it. your Canon 35/1.4 II stopped down to F2.0 will be running circles around the zoom lens.
While this is true, the 35mm isn't nearly as versatile. I get very good images from the f/2 wide open and it will be used outdoors nearly all the time, sometimes in natural light and sometimes with flash. It is very rare for me to shoot wider than 50mm. 99% of the time I'm shooting portraits and fashion. Older women, especially at close distance, do not appreciate ultra sharp images.
Yes, I know I can soften things in post if I need to with the texture or clarity sliders, but that isn't an ideal solution for me. The RF 28-70mm covers 35mm and 50mm for me and even gives me a very acceptable portrait focal length at 70mm. My RF 85mm can handle all my indoor work, and it is unbelievably sharp even at f/1.2. Right now I am waiting to see what is going to be offered in a fast zoom (Hopefully a 70-135 f/2), but that will be a long wait. If a prime 135mm f/2 or faster is offered first, that will be all I need and I'll probably forget all about the longer zoom. I'll attach three photos. The first with the EF 35mm f/1.4L II wide open with a young girl who has perfect skin, and then the RF 28-70mm f/2L at 70mm wide open with a model who is in her late 20's. The 35mm is awesomely sharp. I'd have kept it, but needed to sell to begin the switch switch over to RF lenses. I may still also get the RF 50mm f/1.2L one of these days (after getting a longer prime or zoom, but for now the 28-70 is very good). The color photo is also from the 28-70 wide open, I had to selectively soften so few small areas because of makeup caking. I also softened her nose ring which was razor sharp just because it was a quick edit and is a casualty of the softening around her nose due to makeup caking. So I cannot see enough of an advantage for keeping the 35 except for it being faster. The color photo is also a huge crop from a nearly half body shot with lots of space above her head.