Unfortunately? This is purely for nostalgia, so using the new character assets would make no sense. All they need to do is support higher resolutions and we're in for a treat.
Making a nelf hunter and reliving 2005 all over again.
I agree that it is unfortunate. There is literally no reason not to give players the option to use the modern character models for example.
I would love to have the classic experience with modern art assets. It's all client based anyway.