I think they're looking hard at the .327mag or a six-shot model. The weight will change, but it looks like there's a lot of room to beef up that cylinder.
With something as "radical" as a polymer framed revolver, they're dipping a toe in the water with a more traditional 5-shot .38 first. I think going to .327 Fed. Mag with the rollout might have been "too much, too soon" etc. for the Ruger marketing people to think it would fly.
Frame stress could be an issue, but I'm sure there's metal stiffners in there to begin with, no?