Anyone know if there has been (or will be) any model kits of the AH-56A Cheyenne attack helicopter?

Yes, Aurora made one in 1/72 scale from 1969-77, and was kit #502. Couple of different boxings, reportedly one of Aurora's better kits. I believe the molds were lost in the "Great Train Wreck" of 1977. They pop up on eBay from time to time, but command a hefty price.

Someone does a resin kit of one, but I don't remember who or what scale. I do remember that it was pricey and hard to find.