If you wanted to experience Call of Duty: Modern Warfare Remastered without purchasing the upcoming Call of Duty: Infinite Warfare, it seems that you sadly won't be able to.
According to Activision's official FAQ for Call of Duty: Modern Warfare Remastered, it will not come on a separate disc. Instead, it is a "full game digital download that will be included in the Legacy, Legacy Pro, and Digital Deluxe editions of Call of Duty: Infinite Warfare." And more specifically, "you must own Call of Duty: Infinite Warfare in order to get Call of Duty: Modern Warfare Remastered."
It's disappointing that Modern Warfare Remastered won't be available separately since it would seem that as a digital release, where an internet connection will be required, it would be easily distributed as a distinct entity.
The FAQ confirms that Modern Warfare Remastered will feature the full campaign and include the 10 multiplayer maps from the original game, enhancing it all with HD graphics, textures, lightning, and rendering. The game will have dedicated servers and maintain the original game's movement system.
Developed by Raven and executively produced by Infinity Ward, it will be available on PS4, Xbox One, and PC.