Bring on the R5 and I will use my 135L with it.I have used 5D's for a long time now... I am waiting to see how this develops, but would love to see 135mm f/2.
I usually use 5D mark III, 50mm 1.2 and 135mm f/2 90% of the time.
The 28-70 2.8 doesn't seem like a replacement because of the weight.
But bring on the 135L and I will probably change systems.