I hadn't until my sons and I let it run through.   We were surprised by the scene and what it might mean.   The scene is after the credits, so if you haven't seen it, let the credits roll all the way throught.

Havent played it in a few months but you talking about the scene with Cortana and the Flood/creature?

I've watched it a few times.  Not sure if Cortana was somehow maligned & became evil, since she apparently seems ready to tell-all to the Flood Gravemind.  Maybe being left stranded behind pissed her off? I dunno. So I'm thinking the Gravemind might make a return in the last installment, possibly as some sort of uber boss.

Quoted: I've watched it a few times.  Not sure if Cortana was somehow maligned & became evil, since she apparently seems ready to tell-all to the Flood Gravemind.  Maybe being left stranded behind pissed her off? I dunno. So I'm thinking the Gravemind might make a return in the last installment, possibly as some sort of uber boss.

Or she could be fishing for information.  Hell, she's stuck there and as she said earlier, this is probably one of the strongest presence she has ever dealt with (far more complex than any covenant AI).

She was selected for a reason to be part of the spartan program, primarily of her intelligence and strength in dealing with AIs.  Seeing as the gravemind is truly an AI, but more of a "conglomeration" of information, it will be interesting to see how Bungie unfolds this part of the story line.

Just hope they don't screw up the next installment like they did with #2.

Quoted: Havent played it in a few months but you talking about the scene with Cortana and the Flood/creature?

Yup.  My boys and I never even knew it was there.