There are no updates that can make this a good game. What are they trying to achieve by continuing to work on it? Nothing will get players to return to the game.
Might be the matter of looks and prestige. This was a major Xbox exclusive (or it was at least taken as one) from a developer that was, prior to it, a critical darling. Much like Square Enix wouldn't let FF XIV fail as it would be a
really bad look for them to have a numbered FF entry and a new FF MMO be a failure, so they invested loads into redoing the game, maybe at MS they are looking at Redfall as something that oughtn't be allowed to be remembered as a failure if they can help it. I can't see them going the same lengths as SE but I can see them investing in some enhanced edition that should salvage the game's reputation. Just think on it, if it was a major update/overhaul freely available to the existing owners, it would certainly get them some positivity.