They will probably make it $450 with a game officially, or $400 without a game and still packing Kinect. Unfortunately for MS they can never go back to $500. Stores lowering the price on the Titanfall bundle has set a new price of $450 with a game, and MS will have to continue that value, or sales will drop off a cliff. I see them selling the Titanfall bundle for $450 until stock dries up, and then they may have to either make a new $450 bundle, or drop the price of the standalone unit to $400.
MS's biggest problem isn't price at this point though, it is games. The system with Titanfall at $450 is a pretty good value, but unless there are must have exclusives then there really isn't a whole lot of a reason to jump on it. I have thought about picking up the bundle a couple of times, but when I stop and think about what I would actually play on the system, I decide to hold off on it. With all multi-platform games pretty much guaranteed to be worse on the system, MS has to sell their console almost entirely on exclusive features and games. When you look at what is on offer, there isn't a whole lot there that screams "must have" IMO. There are some decent games for sure, as I would like to play Ryse and Dead Rising, but not enough to buy the system. Those are more of games that I would buy for cheap later on down the line when I get the system for another game.
When I think about future exclusive offerings Sunset Overdrive is the only thing that comes to mind for this year, and that just isn't enough to get me to buy a system, and most consumers won't have even heard of it yet. E3 is going to be incredibly important for MS, as what exclusives they show for this year are going to have to be system sellers.