Nothing to be afraid of. Windows is used on many special and secret devices, manufacturers customizing it a lot, but it doesn't mean normal customers can't use windows. Same for SailfishOS: OMP and other structures will provide special software and services for SailfishOS, but OS code will not be modified to include these changes, it will be only prepared to allow manufacturers to customize SailfishOS on their devices. Normal customers will never see it on global market devices.