For those who are wondering about it, yes it appears that is indeed the case as Activision has since confirmed it in a FAQ published on its website. According to the FAQ, it reads, “Call of Duty: Modern Warfare Remastered is a full game digital download that will be included in the Infinite Warfare Legacy Edition and Legacy Pro Edition on PlayStation 4. The digital download is redeemed via a voucher code on an insert in the box. The Infinite Warfare game disc must be inserted to play Modern Warfare Remastered. Internet connection is required.”
This applies to both the PS4 and Xbox One. As for gamers on the PC who plan to purchase the game through Steam, “A Steam key will be provided in the Legacy Edition of Infinite Warfare that will provide access to both Infinite Warfare and Modern Warfare Remastered. Internet connection is required.”
Basically at the end of the day, gamers will still need to own Call of Duty: Infinite Warfare if they want to get their hands on the remastered copy of Modern Warfare. Will this change in the future? It doesn’t look that way, so if you absolutely have to have it, then this is the only way to get it.