As I have stated several times here, a paintkit has been in the works, and it will be released when the very next product is released. Things are always quiet during the middle of projects. The time that has been invested in the paintkit, which covers every single one of the variants through both of the warbird-related P-51D products, and the coming product, is the reason why it has taken as long as it has, and cannot become available, yet.
(It's much easier when you only have one visual model or P-51D type model to cover for a paintkit, but the eventual paintkit will cover up to 20 models or more in total, so that whatever scheme you wish to paint, modern or historic, you can apply it to the best visual model/P-51D variant suited. Remember, that besides a perfect P-51D-30, or a P-51D-20 (with numerous differences between them), we have included the only available F-6D for FSX, the only tall-tailed P-51D's for FSX, the only P-51K for FSX, the only dual-seat P-51D's for FSX, and all of these variants, on top of the others not mentioned, require subtle changes between one texture format to the next.)
I've hinted a few times as to what will be included in the next product, and for those who have that book that is linked to at the beginning of this thread, it will come in handy (though with only one aspect of the product). We aren't 'only' interested in modern warbirds, as will be shown shortly. If you don't mind being 'teased' further, perhaps I can put up an image or two from the product, before it is released, though there is still a lot of work to be done.
And to hit on another topic, everyone who has seemed to have wanted a paintkit for the Warbirdsim P-51B/C's, has contacted me either through e-mail or through private message, and has gotten a copy of it. To date, I have sent out more than 20 download links for the paintkit.