but if not a post-game arc, then what?
mid-game addon will completely ruin the mere semblance of urgency that is left in the game. Hearts of Stone, while could be played earlier in the game, are locked to a higher level which many players will only get after the Isle of Mists - which is, I would argue, the main (if premature) climax of the story. the urgency of TW3's acts 1 and 2 rests on finding Ciri, and when she's safe the Hunt doesn't really feel all that dangerous and imminent anymore. this way going to haunted mansions and weddings all of a sudden doesn't feel too jarring (that said, considering O'Dimm can give you pointers on how not to get her killed in the end if you ask how to find her, HoS can be played canonically as a part of the search for Ciri, but it just makes the whole ordeal unnecessarily more videogame-y with its pacing).
since Cyberpunk doesn't really have a 3rd act like TW3, and there is no way to fit dlc in the middle of the post-PNR events believably, I, at least at this time, can't imagine them making the mid-story addon work.
a prequel dlc similarly doesn't look all that plausible. they would have to create 3 different scenarios for different life paths, but they couldn't even be bothered to make a somewhat coherent prologue with them (and with Padre remembering you later on).
that leaves either post-game dlc, a spin-off dlc or an "Operation: Anchorage"-type dlc. if they decide to do the latter, god have mercy on their souls, VR-missions-dlc weren't popular even in better times.
a spin-off dlc can potentially work incredibly well (Daud's dlc in the first Dishonored) or turn into an insufferable fanservice and retcon festival (Death of the Outsider). considering that here the only plausible candidate for a spin-off is Johnny, and how many people don't like the guy, I think CDPR should realize that they are going to alienate a lot of players with a Silverhand-centered story. we might get one of those, but since they've said "TW3-style dlcs" I expect multiple addons (unless they ONLY meant free dlc with the cut features).
now, to come back to what you've said about NightCorp - it would be cool to see it. another theory I've seen thrown around here is NUSA's involvement. there is also this incessant news report in the game telling that about >80% of NC residents wanting to re-integrate. maybe this is going to be V/Johnny's Last Big Job - to overturn the NCexit and (try to) kick the corporations out for good. considering how TW2 altered the map of the North for the Witcher's universe, it would be fitting for CDPR to do the same for Cyberpunk's canon as well. also, politics, CDPR love politics.