I personally hope for an all WW2 film.. despite whatever costs are implied with a period piece, I think that thematically, Cap is better served with the first movie dealing with his origins and WW2 battles.. to put it another way-- a studio is probably going to want the movie to be 2 hours at best.. so does that mean that his origin and first battle with the red skull have to be under 50 minutes? then the ice accident, then unfreezing and fighting red skull or whoever-- in the modern day for the last hour?
To me, that's what RUINED the 1990 cap film, trying to squeeze everything into 90 minutes..
another option, I'd say would to be make the movie "all" in the present, and only have occasional flashbacks to the origin--
Also-- since, presumably, Cap is set up as a franchise, they can film two movies back to back or concurrently, so the filmmakers have a clearer idea about the overall arc they are trying to convey...