I believe there are 22 fretters and P-90 versions in the works, but nothing confirmed as yet. I don't even know if the maple tops are new standard production guitars or a special run.
Re. the scratchplate, it's the way it is as apparantly PRS may dabble with the configuration in the future. They then don't have to worry about body routing etc as it's all on a scratchplate.
I like the Mira just as it is, no maple top and all. But that blue one does look incredibly tasty to my eyes...