Sadly, they sold it off to Take Two Interactive who botched the 3rd game in the series and killed off the franchise.
I wish I could buy the IP off of Take Two and revive it, but until then I just have to settle for playing the modern ports that are still being maintained.
Also, we should play Destiny. Not to turn HN into LFG or anything.
I'm the one that makes everybody install it to play it for the first time so that everyone can experience the agonizing embarrassment of their best laid plans being thwarted by their own dwarves accidentally decimating themselves by throwing their molotov cocktails straight up into the air. "<BANG>... Casualties." followed by the inevitable, "Argh! What?!? Noooooooo!"
Never gets old.
I doubt Sony would ever sell them. :)
But yeah, it’s hard to dissociate Halo from Bungie and Microsoft.