I think halo infinite should add a playable brute, elite , and grunt story as well as add it to multiplayer like old school halo 2
Hey OP, there are no plans at the moment to add other playable races to Infinite but you’re welcome to add your thoughts to existing discussion thread 
https://www.halowaypoint.com/en-us/forums/6e35355aecdf4fd0acdaee3cc4156fd4/topics/sangheili-elites-in-new-trilogy-matchmaking/ff89aca2-5e7e-489b-98ae-c58513f99227/posts