I'm sure there will be a ProMaster market for Bs but with current vans if you are going to spend a minimum of $80,000 plus I am still going to be in the market for another Sprinter as long as I can afford it. I doubt there can be much more than $10,000 base difference. The only thing attractive about the ProMaster and its siblings is the extra 3" width. That could be precious but at the same time I don't want to be much wider than what I have. Length wise they seem to be in an awkward length compared to Sprinter offerings but may have greater appeal by staying under 22 feet. The elevated cab floor is going to be a limiting design Achilles heel, IMO. I don't like that at all. So far most designs I've seen have awkward transitions and design limitations.
Of course, I'd have to drive one to compare to a Sprinter but right now I have a hard time seeing where a ProMaster van would have any quality, handling, comfort or driveability advantages over a Sprinter. Few in America can express an opinion about that at this time.
Pluses? Well, it definitely could open up new ideas and design features for Bs of all makes. Shaking the bushes so to speak. Also, I would never consider the ProMaster from what I've seen so far until I see the final off the line Ford Transit.