According to the most recent video from Ubisoft, Assassin’s Creed Mirage won’t have XP-based character levels! That means no grinding to reach certain levels, but more importantly, it means no grinding to unlock certain abilities.
Abilities themselves are tied to the story progression, which makes sense; Mirage focuses more on the classic Assassin’s Creed gameplay, which means focusing more on classic Assassin’s Creed story progression.
Story delivery is a critical part of the game here, so tying in ability unlocks to story progression makes a lot of sense.
I will note that there is still a skill point system, but we can assume based on what was said that these skill points are rewarded as part of story progression.
Ghost of Tsushima operated on a similar system, and is widely considered to be a spiritual successor to the AC series (or an AC set in Japan, if you will).
Progress in the game is also apparently tracked via ranks in the Brotherhood; As you progress you’ll gain skill points, unlock new cosmetics and abilities, and tools (which can also be upgraded, much like Ghost of Tsushima).
Watch the full video from Ubisoft below.