I'm hoping Hellblade 2 is well received and is a strong successor in the franchise with a suitable expansion of gameplay systems and dramatic encounters, but in response to the OP...
Going by signs of how play works in the trailer and what they've talked about the game being, it is not going to be Xbox's most important exclusive.
So far, Hellblade 2 seems to be a large-scale version of the intimate, indie concept of the first game, which had niche, specific appear and turned off a lot of people expecting a GoW/Dark Souls level of scope and play depth. This sequel is showing a great expansion over the first game, but it's still doing everything so many people didn't like (single-enemy encounters, events based on emotional resonance rather than player challenge or combat depth,) and it's not showing major new elements which would attract some kind of third audience who aren't already sold from loving the first game or out from hating the first game. Also, it looks great, but MS has many other studios already working on mastering UE5's new abilities (The Coalition is its vanguard team even though Hellblade 2 was announced first, and Coalition has actually shipped a UE5 project since it worked on optimizing Matrix and also was an early Epic partner for Xbox development support and
Alpha Point testing,) so I'm not sure Ninja Theory's industrial knowledge is going to trickle down in a significant way? (Ninja Theory are doing other things with scanning and performance capture that might trade around offices, but they're using MetaHumans and Quixel assets and other things that are simply base to UE, not necessarily cutting-edge stuff that nobody else has access to.)
Hellblade 2 will be a mile marker in the Xbox Series lineup just in that it finally completes the promise of the new console announcement from 2019, and also a major release on the important UE5 tech. In terms of sales and user base expansion, though, I would be very surprised if this game changed anything for Xbox at this point. A second Hellblade is a great feather in the cap, but not the type of thing which a publisher would want to stake its future on. (And they're not, so it's fine, this is just another game in the pipeline.)
...It also is not the "most hyped game ever". It just has a very, very long tail of promotion because MS showed it off way before it was ready. Each showing has been an encouraging but somewhat muted response in comparison to some other top-tier products shown at those shows (the full gameplay reveal at the
last event had 8 pages of responses, which is good but significantly less than either the Wolverine teaser or leak clip, and the neg-to-pos ratio is usually not in the game's favor.) And MS and Ninja Theory haven't done much promotion of the game besides showing progress reports or a snippet once a year, aside from sharing some Iceland travelogues. (MS and NT have actually been respectably tactful in not overhyping this over the years, after shooting it out of a cannon at TGAs in 2019 and then doubling up with the announcement that it would use UE5; since then, the showings have been suitably focused and spaced out, without over-promising anything that the game can't become and usually without trying to position it as the Next Big Thing for mass market gamers.)
"Now that Ninja Theory is part of Xbox Game Studios, that valuable asset now belongs to Microsoft, and now that the shoe is on the other foot, it's imperative that its exclusivity becomes as important to Xbox as its predecessor was to PlayStation."
Uh, article writer, if you have to remind us because it is so easy to forget that the first game was "exclusive" to PlayStation, (more that it just started in the most profitable target markets before expanding outwards, and that PS Blog gave it some extra visibility since it ran the Dev Diaries and other pieces; also, it came to PC same day as PS4,) maybe it wasn't such a valuable asset important to the previous platform?