Tronsky,
It's not confirmed the P-61 is ever coming, but since so many people want it, we'll probably see it someday.
******
CavemanJ,
My understanding of the perk system is that one of its functions is to reduce the number of historically rare Uber-planes we see in the MA. Hence, the P-51D, La-7, and Fw-190D, although superior aircraft, are not perked, in part because they were used extensively. But the Ta-152, some F4U models, and the Spit XIV are perked because they were rarities in combat.
This doesn't seem to apply to GVs, since only 70 (!) Ostwinds were produced in WW2.
MRPLUTO