I have heard they are not getting many offers for Wall.
The problem is, his contract is about half right now what it will be in the summer, making him a lot easier to trade now.
I'm not sure why people think Wall has value. He doesn't have any as a result of his contract AND his play. The guy will put up raw numbers, but he has awful shot selection, dribbles the air out of the ball, defense is a 50/50 proposition, and plays with inconsistent effort. As a result the Wizards consistently play better when he's out. To read that people think that they'll get a 1st rd pick or a Dennis Smith for him is laughable. The Wizards will be the ones that will have to add assets in order for someone to take on Wall in a salary dump.
The Wizards aren't getting many offers, since ownership/management isn't really ready to break up the Wall/Beal partnership.
They see that things aren't going like they expected and have (probably) made the decision that they are open to make a change. Either trading away Porter for better role players, or trading away their franchise player for a another All Star or a package built around an upcoming star to rebuild.
In their view there haven't been good enough offers on the table to give up what they have: an underperforming team (with 2 All Stars) that still has a shot to make the playoffs. I don't think they're aware how dangerous it is for them to do nothing. And trading Oubre + Rivers for Ariza is still doing essentially nothing, but I'm sure they also don't realize that!
A GM that signs Mahinmi for 64/4 and Wall for 170/4 definitely isn't someone that looks longterm.
It most definitely is in the Wizards' interest to trade Wall before his extension kicks in. And they should listen to any offer they get. There's probably a chance to get something valuable out of a deal as well (a young player to develop, mid-late 1st), but the most value is to not cripple your franchise! Wait and they indeed have to give up assets to get rid of Wall's deal.
I believe Wizards' management will not be able to realize the full extent of their situation and continue this road and they'll burn for it. (And I will enjoy it)
Why should any other team trade for Wall then? Because in certain situations he could make a team better, where the rewards are greater than the cost. For example a team that has an All Star and wants to make an ultimate push for a title (examples: Lakers, Pelicans), an expensive mediocre team that needs improvement (examples: Pistons, Heat) or a team with a lot of cap space in need for a Point Guard (examples: Knicks, Suns, Magic).
So I think there could be a market for Wall if the Wizards are able to be realistic about his value.