Odds are that decision will come down to whether or not MS thinks the increase in sales will be enough to counter losing $50 in revenue per console.
If they think kepping it at $349 will get them let's say...90k units a week, vs. Let's say 60k units at $399. Than they might say that's a worthwhile sales increase. But if it's something more like 75k vs 60k, it may not be.
Bet with Adamblaziken:
I bet that on launch the Nintendo Switch will have no built in in-game voice chat. He bets that it will. The winner gets six months of avatar control over the other user.