Honestly I didn’t give a shit about Halo 5s story when the gameplay was fucking superb 9/10 times.
Warden Eternal is cool and I hope they do more with him. The story ending with !>Cortana basically winning<! Was actually interesting as next we’ll see the Created at full strength under her leadership. We’ll also likely see more of the Arbiter, Halsey, Rtas’ Vadum (Elite from Halo 2/3 missing their left mandibles) maybe? I hope.
Then of course Installation 09 from Halo Wars 2, the Banished and possibly a return to the Ark and the Spirit of Fire finally being recovered by the UNSC. The Banished stuff on the Ark happens just after Halo 5 as well so the timeline matches perfectly.