Before that, their online store has had them on permanent "back order" for years. Nintendo didn't exactly support it when the cube was still manufactured with the port. It is very unlikely they will bother now.
I guess it depends on the game and personal experience. For example, F-Zero looks better on hidef. However, Zelda Wind Waker actually looks worse. The crude simplicity of the character models stand out with sore jaggies that were not apparent on a normal tv. The blur filter helped a lot to hide this flaw, but not so much on hidef.
What I have noticed is that HDTV support in games has steadily dropped. It is not as supported as it was before the model revision. Most games that provide hidef are from the early years. Another interesting bit is that there is not one 1st party Nintendo game that offers widerscreen mode. You get 480p but no aspect correction.
Very poor indeed. Supposedly if you call their customer service you can arrange to replace your hidef challenged cube with the older model that has it. Don't know if its true though.