In the documentary Remaking the Legend it shows quick snippets of Locke in some dark chamber with some Sangheili Where are these guys? Where do you think he is (Sangheilos, some ship), and do you think Thel is there in this meeting? It looks like there’s other Humans in this meeting, who do you think they are (I think possibly Blue Team)? I’m sure this is going to be setting up the conflict in Halo 5: Guardians.
Absolutely no idea.
What I’m more interested in, is that he’s not the only human in the room. There’s another Spartan over his sholder with the same helmet but with a red visor…so maybe Locke now leads an ONI Spartan team??
Also, the Elites he’s meeting are wearing Covenant elite armour, not the kind we saw in H4. Meaning they look organised and well armed/ armoured. There’s also at least one other elite there.
I’m going to assume he’s at 'Vadam Keep.
It’s all just speculation at this point.
Play Halo 2 Anniversary and watch cutscenes to find out.