Not really, they will still be much bigger due to retrofocus than a dedicated mirrorless lens. Lens redesign is needed really to make the most of it.
Pros are going to be very reluctant to start buying several thousand dollars of lenses in a new and unproven (longevity-wise) lens mount, but may well buy a $1000 camera if an adapter lets it accept all of their existing lenses, keep the same focal length, and also turn their 16-35mm f/2.8 into a 16-35mm f/1.8.