As revealed in a deleted scene from Spider-Man: Homecoming, Miles Morales is 100 percent confirmed to exist in the MCU.
Kevin Feige spoke during the press tour for Spider-Man: Homecoming about the existence of Miles Morales and was vague about it, but did more or less say the character exists.
It is also worth noting Sony is also currently working on an animated Spider-Man movie that will have Miles Morales as the main character, but that movie won’t connect to the MCU in any way.
Spider-Man: Homecoming brought the original Spider-Man into the Marvel Cinematic Universe over the summer in a big way, following his glorious debut in Captain America: Civil War.