I doubt anyone really knows at this point, not even the folks at CDPR. Usually how this works is that everyone works against these targets and tries their darndest to hit them, but then unforseen things happen and boom, you're confronted with either shipping something that's a bit broken (with usually the hope that you'll patch it a few days after launch) or delay the launch so that bugs can get ironed out. What should be pretty clear is that nobody takes these decisions lightly, so the game is probably not in that great of a state right now, otherwise there's 0 chance they would've delayed it again so close before release. I also doubt it's just performance, cause they probably would've been okay with the game not in the greatest shape on base consoles. My guess is that there's still quite a ton of bugs open and they just couldn't get them down to a number where they felt okay shipping the game and patching it after. So really, it's anyone's guess, it's highly dependent on the severity of the bugs and whether or not their folks still have enough braincells left to get the highest priority bugs fixed until release.
With how much is at stake for them, I'm glad I'm not in their shoes. There must be tremendous pressure on everyone trying to finally get this thing out of the door.
