Just in case you were worried you'd miss your chance to unlock Spartan John-117, also known as Halo's Master Chief, aka John Halo, for use in Fortnite, please worry not: You can still do that into the indefinite and unbidden future simply by playing on an Xbox Series X/S console. So, yes, if you need to dress up as Master Chief (in matte black) so you can kill Goku or Peter Griffin or whoever else... it's still available.
Assuming of course you have an Xbox Series X/S to play on.
The confusion stems from a December 23rd tweet from the FortniteStatus twitter account that [[link]] said the skin would be [[link]] unavailable starting, uh, December 2024. Which weirdly meant that you would have been able to buy it for 23 days but you'd be forced to return it.
Anyway, vigilant users quickly noticed the error because, as 
Epic said back in 2020 when announcing Matte Black Master Chief as a skin, you'd be able to get it in Fortnite at any point in the future and there would be "no time limit for unlocking this style."
"We apologize for the confusion from our previous tweet saying it was no longer available," said Epic the next day. A Christmas Eve miracle, I guess. Or one more just-in-time victory for the one and only Master Chief. Or both. Anyone's guess at this point. Maybe the plot of Halo 7 will be MC trying to stay in Fortnite ala Wreck-It-Ralph.
Xbox Series X|S after acquiring the outfit to unlock the style, and this will remain available as an unlockable style for playing [[link]] on the platform in line with our original post. We apologize… https://t.co/cKKghrPfXk pic.twitter.com/eJGHfvqfmG