I don't think anyone inside has realistically assumed Henry was ever coming back for next season. That's been the assumption I've seen since January. Could he always have a change of heart? Sure. Who knows what it would take for that to happen, and honestly I think it's the slimmest of possibilities that should not ever be counted on. If he were to come back, I think it would be a welcomed, but unexpected surprise to management. They've probably operated much of this season under the assumption that it'll be a cleaner slate next year in terms of personnel.
As for a sale, it just doesn't make sense why it would be happening now. In a year or two? Who knows. A lot can change between now and then. But it doesn't make sense from a value stand point why to do it now. Word about previous losses is way too public (not that a prospective buyer wouldn't have a clear picture of the team's books prior to a sale regardless, but still), roster uncertainty for next year as it related to the star players (like Henry for example), etc. The negotiating power for Red Bull would have taken a bit of a hit and it is still a growing league. They're better off holding it, getting their deficit under control, establishing more of a future structure roster wise so it doesn't look like a bottom feeder team (as we know attendance will get worse if they are, which in turn cripples revenues), and allowing league interest to grow a bit over the next 18-24 months and then sell it off if they're so interested. The value of the arena will always depreciate, but that's going to happen regardless. It just doesn't seem like the right time to sell from a business perspective from their end.