Minor changes. The 360 controller reinvented the Xbox S controller into a magnificent, ergonomic machine. They may alter little bits here and there (adjust tension on triggers, change feel/look of thumbsticks, nuke existing D-Pad and start over), but considering how "share" happy the world is getting, I wouldn't be surprised if Microsoft did something similar. It may be a button, you may be yelling at your Kinect. Depends on how crazy Microsoft is.
No more Points. Gone. Now you can pay in real money.
Rethinking how they double-charge "premium" services ("you gotta pay for Gold, so you can pay for Hulu to watch your TV shows"). To best satiate critics and gamers alike, I see them introducing some sort of tiered system. Pay little (or nothing) to access apps (especially the already-paid-for apps, like Netflix and Hulu), and bring the cost down of the yearly Gold subscription. If no price adjustments, then they'll go crazy with PlayStation Plus-like features, like discounts, free games in your library, etc., etc..
An extreme - and one I don't see them doing - is partnering with these paid subscriber memberships, to offer a "sign up for Gold, get this service for free*" thing. That asterisk is for "but only on the Xbox".
Achievements should see a new coat of paint, as well as Beacons, Friends List, and social gatherings (Parties, Voice Chats, etc.).
This is the reason why Nintendo didn't make the Wii remotes for the GameCube, as they initially planned; they couldn't bank on everyone who owned a GameCube to run out and buy them, which would limit developers. Knowing a system has this hardware by default, developers aren't limited. Just look at the hard drive/Arcade debacle early on in the 360's life.
We know my stance on the name - Xbox Infinite/Infinity - and the reason behind it makes perfect sense (in Microsoft's world). The reason the 360 is named that is because you approach it, and do a complete circle to walk away.
No. Microsoft named the 360 this because it put you at the center of what entertainment the system offered. Naming it "Infinite" or "Infinity" makes sense. Take a 360 degree circle, add a second one right next to it (to indicate "360 Two", and you get the infinity loop. It's also the same if you take '8' from Windows 8, and slap it on it's side. Microsoft can run with this name under marketing campaigns of "Infinite Possibilities".
Don't expect much on Tuesday. We already know Call of Duty: Ghosts gets its official reveal on that day, but as far as bomb-shells, or major reveals, they're going to wait until E3. They're going to get the hardware out of the way early - much like Sony - and focus on games later.