The problem for MS now is that there isn't any wiggle room for price cuts anytime soon as the console is already dirt cheap and they just reduced the price. They already tried to undercut their competition in price without much impact so any additional price cuts to boost sales will devalue the product. Now they can only compete in actual content, you know, by releasing actual games. Starfield better releases sooner rather than later as the sales of the Xbox consoles will come to a screeching halt. They better not release Starfield in November. Yes, "pre-season" is important, not only in the holidays.
That's the usual problem with the constant promotions. The product gets devalued, people just won't buy it again at full price.
The biggest problem is when the product doesn't sell really well even with the promotions. At that point the price lever is gone for you, you know that price isn't the problem.
The reality is that people won't buy consoles just because of a cheap entry price, they need reasons and those reasons are big games.
About Starfield it all depends on Microsoft having something else big planned for the next holiday season. Right now that doesn't seem to be the case, Hellblade and Avowed might be their next games (and it's not even clear if they'll be ready this year) but these are not system sellers. Competition already has a huge system seller announced like Spiderman 2. Under these circumstances it's only natural to invest in Starfield as a big holiday title while polishing it even further. We'll see what happens but honestly a Starfield delay not only wouldn't suprise me but it seems almost logical.