I don't have a source but Disney has listed some of her merch as Disney Princess merch and does a coronation for all their princesses so it's most likely what will happen.
@Lapinlagomorphe yeah, that's what i thinking. Her 11-inch classic doll is part of the Disney Princess Classic Doll Collection. And if you search "Disney Princess Collectibles" on shopDisney's official website, you will see the "Raya Sketchbook Ornament - Raya and the Last Dragon". So Raya will be an official member of the lineup.