Outed by an Irish toy website, Smyths, there was briefly an apparent reference to Halo Infinite - one of sixteen Xbox Series X launch titles, being free-to-play.
On first reading this I thought it meant that Xbox Live Gold wouldn't be required, but it doesn't exactly clarify that, more likely it sounds like parts of the online experience of the game itself will not require purchase at all.
It wouldn't be that surprising really, if it was just that, many games these days such as Call of Duty and Fortnite have a free online component and Microsoft certainly has the room to give amazing perks as we have seen with Gears of War 5 and the extremely economic Game Pass that will replace Gold soon enough.
We will have wait and see, although I don't think I will get a series X myself as I barely use my Xbox One X and I am not sure the vertical monster will fit in my cupboard.
UPDATE: Official confirmation from @halo on Twitter:
But again, is this a free game or free service? Only time will tell, apparently!
Source Leak suggests 'Halo Infinite' multiplayer will be free-to-play | Engadget