The most important things to me, from a first party perspective, is firstly that Halo Infinite needs to meet expectations. This needs to be a full return to form. Period. No excuses. MS also needs to announce at least one new AAA IP. Whatever else you wanna do with existing IP in your portfolio, gamers both inside and out your ecosystem have been frustrated with your lack of new, high profile IP for ages now. Gotta show that you're listening to that feedback. If you deliver on those two things, I think everyone becomes a whole lot more receptive to whatever else you're doing around that.
As far as third party content is concerned, I think I actually have a pretty good idea of what we'll be seeing.
If the Mass Effect trilogy remaster is really happening, and launching early next year, then we're going to see it at this event. EA likes a healthy marketing lead up, and MS has past ties to the franchise. It just makes sense.
MS isn't going to get FF on stage, but they'll wanna show that they continue to have a good relationship with Square, and Square has mentioned having more games to announce over the summer. We'll probably see the next Tomb Raider revealed. Again, MS have a history with the franchise on their E3 stage. Every single game in the survivor trilogy has shown up there, and it's likely this trend continues.
MS has also been partnering with Rockstar a fair bit lately, having first GTA5, and then Red Dead 2 on GamePass. I think we'll see them showing support here in some capacity. Maybe they'll reveal the rumored remake of the first Red Dead...maybe it'll be some minor thing like Sony started the show with...either way, there'll be something.
We've yet to see this year's CoD, which means it'll either be shown here, or at Sony's August State of Play. However, I think Activision would have been at Sony's big June event, if they still had the marketing partnership, not a more low profile State of Play, so it stands to reason it'll be at the Xbox showcase.
CDPR has been featured at the MS E3 consistently. They'll be here, showing another Cyberpunk demo of some kind. Whether that's simply new footage, an early look at the next gen build, or even a glimpse at the eventual multiplayer component, I think we can all agree that they'll be here.
Ubisoft is doing their show on the 12th, and they're likely going to have a big Valhalla blowout, so I don't expect MS is interested in having too much overlap there, but MS does enjoy bringing all the big publishers out in some way, shape, or form, so perhaps they can convince Ubi to hold something or other back for the Xbox showcase. Ubi's own teaser focuses heavily on AC and Watch Dogs, so maybe they can save some Beyond Good and Evil footage for the MS event. Seems like a game that might benefit heavily from next gen advancements.
Elden Ring will get a gameplay reveal. It was revealed at the MS E3 last year, we've seen nothing more of it since....it's time for FromSoft to show the goods.
We may see Remedy's Crossfire X story mode revealed, depending on how much effort has gone into it.
If Dying Light 2 isn't in complete development hell at this point, it may make another appearance.