I believe there's a good chance DFHack itself will adapt, but the UI changes of DF with its various grids will result in the need for some serious work by competent people to make UI functionality work with that framework. I don't know if it will be possible to retain the script/code facing functionality mostly unchanged, or if it will have to be replaced with something that has to be adapted to use different logic.
I would expect "simple" things like popup windows and general dialog boxes to be able to work roughly the same, but anything that defines dimensions and placement will have to change, either in syntax or in use.
The really scary part is the splitting of Premium and Classic UI. If it is done just using different looking widgets that function the same and take up the same space, that's probably not an issue, but if the implementations are functionally different it can be really bad.
Sorry Salmeuk, you didn't want to be scared, but I think there's a reason to be worried on the UI side of things.
To clarify: I'm in favor of a good UI, so I support the UI rework in principle, but I'm not in favor of doing the same UI work twice just for the sake of retaining a Classic/Premium split. Two different UI tile sets/widget looks is perfectly fine, though. Having said that, a UI that doesn't support key shortcuts is NOT good, regardless of how shiny it looks, and I continue to worry about it being put off until never.