The future may very well prove me wrong, but I (like many) thought that Holiday 2015 was going to be the last chance Holiday, where MS was going to throw everything at Sony in the US.
They padded their lineup, sure, but instead of going balls to the wall like many (including myself) predicted, they were conservative in pricing, which is the #1 factor for Holidays.
Instead of having a Halo 5 $349 bundle (to discount $299 during BF), they did a $499 bundle.
Instead of doing a WW Tomb Raider bundle at $349 (to also have an attractive $299 bundle during BF), they went for a $399 1Tb bundle, not available outside of Best Buy, and not even sold in the UK.
Instead of having Fallout 4, their big 3rd party ace, as a $349 bundle, they got a $399 bundle as well.
Their big fighting horse was a remaster (GeoW bundle) and a Lego bundle (both $299 during BF), to fight against 3 Remasters bundle (UC) and a Star Wars bundle during THE Star Wars year, considering that the PS4 is the more attractive console in general at the same price.
This was the Halo 5/ Tomb Raider/ GeoW remater/ Forza 6/ Fallout 4 year for MS.
If MS didn't want to put up a fight with their best lineup vs a relatively weak PS4 exclusive lineup in a crucial Holiday year ... there is little to no chance they will in the future imo. If the past is any indication actualy, 2016 might just be a slaughter sales wise... (but again things tend to defy expectations sometimes, no one expected such a big Holiday win for PS4 until E3 2015).