True to some extent, but eh, he'd still get you 15-20 goals a season, and who else in the Arsenal team will do that?
What's the point in this entire season if he plans to leave the next one? Why bother to try to build up a team when you know you're not going to use it, especially when somebody new is going to come in and change all that? The board will probably be holding back money from Wenger so that they can entice a top manager with a very nice transfer kitty.
Also, without Henry, Arsenal will have a transitionary period until Christmas or so, just like they did when they sold Vieira. Without Wenger, again, they will probably have a transitionary season. May as well get both out of the way at the same time.