Take a look at a few of the photos over on Zeiss Contax month. I still do not think that "modern Coatings" are going to make a any where near as much difference on this particular lens design as they would on most others, for most shots, for most of the time. Would think that most people who had a nice, unblemished, CLA'd Zeiss Opton Sonnar from the 50's would agree. Maybe not.
I'd think the main appeal of this lens, if they even have the slightest idea of how to grind the glass correctly in their what appears to be little shop, is the fact that most of the nice, original compact 50mm Sonnars are all in Contax Rangefinder mounts, so having this in a Leica M mount might be nice, if it was decently manufactured, and affordable, both of which are open to doubt at this point.
As someone else said, the world is awash with nice 50's, why not make a better, modern, perfectly executed version of something exceptional and unusual: W-Nikkor C 25mm f/4. Maybe somebody could make a modern Topogon that's less expensive than the Leica 28mm version.