Well HiTech started with a fairly late war planeset. P51d, 190, 109, once started in this time frame, it only made sense to continue to flesh out the planeset for that period.
Many of us hope to see early war planes eventually come to Aces High. However it seems to come down to the question of "greatest good". Do you model 3 early war planes (that may be flown sparingly at best in a late war enviorment) or add more late war planes that will see more use?
I have no doubt that we will see the early war spit, hurri, A6m, P40 etc eventually. Just a question of when & how he'll do it.