It's a continuation of the story, but they're dropping the number probably due to a new direction in game design.
My guess like many others is something that shakes up the norm. Mayne nonlinear missions, or something closer to open world, or maybe even something a little like the Destiny model.
All of which I am fine with as long as it's able to be played and reasonably beaten offline and solo, with splitscreen co-op available. As long as that is still possible they can add whatever online interactivity they want.
But if it's
totally like Destiny as in lots of it doesnt work offline, playing solo is discouraged and some things cant even be
done solo, then that would be a
dealbreaker. Eventually those servers will close and the game will become
unplayable for the rest of time. That's not what I want for Halo. Halo to this day is a series I love going back to and playing campaign alone on a lazy saturday or couch co-op with my friends. It never stops being good, and I wont accept a Halo campaign with an expiration date.
But I don't think that gameplay shake ups are the only reason why they're dropping the number.
Stinkles has mentioned this as being a jumping on point, so attaching a number would make the game more intimidating to new people who might think they need to play the previous 5 to understand what's going on. And that potentially ties into story reasons. The ending of 5 makes you think that the next game will
directly follow it, but that doesn't seem to be the case here. This taking place 2 years later makes me think they're sort of going in a new direction there as well. Time jumping to put some distance in between this and 4&5. Still following through on some of those threads but generally starting fresh in a way that does not absolutely
require knowledge of that specific plot line.
A possibility I am excited about but it's exactly what I recommended they do with the series after 5's ending was sort of a dud with fans. I wanted them to quickly move on from what they had going on in 5, not drop it, but sort of side step it early on in the game and go in a different direction. Course correction. And I think that may be what's going on here.