I didn’t see any promethians. Not one Warden Eternal. 
Don’t get to comfortable, I’m sure they’ll come back with a vengeance. Prepare yourself, the Forerunners will return… again.
I think the Prometh’s are definitely going to be turned down a notch. The game should be focusing on The Banished more now.
As long as I don’t have to fight 14,537 Warden’s I’m good
I’m fine with the Prometheans coming back in some capacity, as they almost definitely will, but I much prefer fighting the Covenant/Banished so I hope the story focuses on them.
I feel like Prometheans will return in the game, but they most likely won’t be the main focus, and therefore won’t have as great a presence as they did in 4 and 5.
If they do appear a lot in the game, then I hope they’ve had some tweaking done, especially with their teleporting. Nobody likes fighting enemies with cheap escape mechanics, especially if said enemies are bullet sponges…
Prometheans are fine if they are Halo 4-esque in their gameplay mechanics. Promethean Knights were annoying bullet sponges in Halo 5, like a less fun Hunter.