I was told it does. You just have to list it on the rebate form as a VP9 pistol not the SK. A few members on HKPRO website did it that way, with that direction/statement coming from HK USA and it went through without issue.
With that said, you don't have to use the $200 credit for mags but for anything in the HK store. I bought a VP9 when they had the first rebate of only $100 and I bought some other items with that credit. So, if they have one, you could use the credit towards an optic ready slide.