According to the system specs (which isn't confirmed yet) the next Xbox system is significantly weaker than the PS4. I wouldn't be surprised if it isn't, I think Xbox has good games and all so don't call me a fanboy for saying this, but I honestly think MS is going to have trouble with their next platform. They are going to have to REALLY pull out something amazing if they want to top the PS4.
Not an Xbox hater, I think all gamers are equal and it's just matter of preference (for whatever particular reasons). This is just how I honestly feel about it. I hear they have some new IP's in the works so that I'm hoping that's good because I got tired of Halo.
I don't know, but as a 360 user with a Vita, it'll be really hard for Microsoft to win me over this time around.
I think this conference is what's convincing me to get a Vita in the near future should I decide to pick up a PS4. I'll probably still get whatever Microsoft has as it'll probably be heavily integrated with Windows 8/Windows Phone 8 functions.
But in the end, Valve's Steam wins.