The weird, not very well promoted oddball 'firesale' deals on the X1 over the past few days do seem to indicate that they were a last minute reaction to probably losing the month without doing something.
I think if they had announced a promotion with a big advertising campaign on the Halo 5 release day or so where all X1s sold got free Halo 5 and some XBLG time or something, they would have done enough to win.
As it is, I think it was probably too little too late. Their plans were probably laid out ahead of time without any end of month specials whatsoever because they thought PS4 would still be $399 until some time in November, possibly BF and on. $349 came at an odd time historically, and that seemed to really create a big bubble of sales for Sony that might just have kneecapped the best chance MS had at a substantial victory for a long time, if not the entire rest of the generation.
We have to remember that the past victories for X1 either involved massive deals ($329 with AAA pack-ins, etc), or narrow victories in pretty weak months, against $399 PS4s.
$299 X1s soon? Maybe. But I think that kind of crashes into profitability for Microsoft. As we all remember, $349 X1s lost more than they won against $399 PS4s. $299 X1s would be likely to suffer the same fate against $349 PS4s, particularly now that the 1st party deluge looks ready to strike from 2016 onwards. 3rd party now rules the console world of course, but adding that extra factor is just a tough thing to overcome. And I doubt Microsoft would be willing to do what would be necessary to gain real ground : $249 X1s vs. $349 PS4s. I think that would keep them at 1:1 or better in the USA. Other than the UK, the ROW is dead to the Xbox brand.