What we know about X1 is that the US had a decent number of Xbox loyalists who jumped in early. Since then, it's been crickets, and the numbers have gone from bad to worse. I'm expecting July to look like it's returned to pre-$399 weekly averages of 35-40k/week at best, and perhaps weaker than that.
So the question then becomes : will MS be able to start pulling the non-hardcore in? It's a good question honestly.
Relatively decent software sales to the rabid fans that bought in at $499 is meaningless. The hardcore fanbase will buy anything (as seen by decent sales of meh titles like KZ:SF, Ryse, yadda/infinity). The larger market though, will take a lot more work, and is much more likely to follow the leader.
Holding up the PS3 as some paragon of success in the US is pretty terrible honestly. The PS3 was a dismal presence in the US overall. A VERY sizable chunk of them sold were only ever used as Bluray players. The 360 absolutely dominated the US, and the PS3 mostly existed in the gaming community as the EXTRA system, not as the primary system. That was achieved partly due to the thing not requiring a subscription to make decent use of it. With the XB1, it makes a horrendous extra system, as it's near-useless without XBLG. The U makes a far better (and more affordable) companion to a PS4 and/or PC setup.
So we're back to : Xbox fans need to be convinced to drop 360 and go XB1 instead of PS4. XB1 will sell on exclusives. Multiplats will be a L for XB1 overall, as the de-facto multiplat preferred platform is and will be PS4 from here out (just like 360 dominated multiplats last time).
It's a real bind. I don't see XB1 picking up enough slack to catch the U this year. Smash will catch fire, and I think everyone with functioning headmeat knows that a price cut is in the cards.
A $299 XB1 or $349 MCC/SO Bundle .. now that would make me change my mind and tilt the odds in the XB1's favor a bit. $299 IS a magic number for a flagship console. As much as I like the U, it doesn't hold the 'flagship' mantle honestly. It's more of a niche unit for first-rate 1st party stuff and not much else.