Halo releases have really slowed down so I would be surprised if we didn't get one this e3. 360 had 5 Halo FPS titles, XBO has 2 and we're nearing the end of this generation.
Maybe they finally understood that the quality has been going down since Bungie left so they´re trying to blow people away with Halo 6.
I have very high expectations for Halo 6. I think they know that they have to knock it out of the park next time. XB lost a lot of market share this generation. If it weren't for Halo loyalists, they'd have lost even more. If they go without a mega-hit Halo for a whole generation, it will be even harder to keep people in the XB universe for the next gen.
Forza games have been great forever. I expect that to continue.
Gears..... eh, I dunno. I don't feel like the series is all that important anymore. I certainly don't care about it, personally.