Well, what I want is a more classic Halo experience without any advanced movement mechanic what so ever, especially not sprint. That said I don't want a H3.5 either, some neat innovation is always welcome! Make the game feel faster, weapon up all the time doesn't mean it needs to feel sluggish! Bring back dual wielding (played H2A recently and yes, the balancing is a hue issue, but damn me if it's not fun to use)!
Something Halo did better than any other FPS outside of Source based games is how extremely modular the game is. You can morph Halo in almost everything you want as long as the weapon balancing of the given map allows it. And we have Forge to ensure it allows it!^^ I want Halo's modularity to be a pillar for multiplayer again and I don't think it's possible whit advanced movements forced to the base mechanics, because if that's the case than most weapons won't work well without sprint and trust. Not to mention that vehicles would once again become more important and not just a way to travel faster. Overall I hope to see even more options and personalization! AI in forge, more scripts to work with, destructible pieces and surfaces, interactions with the map (doors, bridges, moving platforms, cranes and such)... With the right tools Hi could really become, well, infinite!
On the SP/Firefight side of things I would like to see a semi-open world campaign structure with secondary missions. To make such a kind of level design work the world must feel alive imho. In other words it needs to be filled with interesting things to see and to interact with, and I mean much more world interaction as well as AI based ones! Soldiers reacting to the surroundings, wildlife acting to your actions and physic based objects to act like "puzzles" to unlock special weapons or get some goodies as well as destructible environments to help you out in battle. I also wanna see a reintroduction to armour abilities, but as pick ups (I want them to be the logical evolution to equipment basically and not tied to loadouts). Long story short, I want to see a quite different Halo, however I would appreciate the evolution to be tied to the sandbox, environment and AI interaction over forcing modernisation upon the base mechanics if that makes any sense!
That's what I want, what I expect however is a different story. The most obvious outcome would be a Halo 5-esk title on a gameplay level, just with a brush of classic paint job over most objects/characters and some minor mechanics like ground pound, stabiliser and Spartan charge left on the chopping board. I guess the campaign will still be half-open world though, meaning you get from mission to mission by travelling the ring, but the actual mission will be a classic level, just with the 343 touch so that everything is going to feel a lot more linear than it should be. I also hope you like ADS, sprint, climber and thrust because those are going to stay imho! :P
But hey! This time we're getting a H5 with the Banished as the main enemy forces and probably the Flood down the line, so at least the battles will be a hell lot more interesting this time around. I'm also sure that the story won't be half-baked again (even though solving the "evil Cortana" plot with grace is going to be impossible no matter what) and the wildlife might be an interesting addition as well! it's just sad that the gameplay will feel like Crysis again and not like a real Halo experience. Maybe we're lucky though and some good Samaritan will mod the yoink out of this with some good ol' fashioned classic gameplay rebalancing. Get Hi for PC is what I'm basically say'n!