I also have given uo the hope that Prime will ever live up to Mathcad.
They sure will add more and more features, but probably not all. But missing features is not all. Ist the overall useability which is a great drawback and I am pretty sure they won't be willing to change the UI significantly. We will get a costomizable ribbon, maybe keyboard shortcuts which work for foreign keyboards, too, maybe even a floating palette (I doubt it), but that will be all. If we have luck we will be able to change the highlighting color and other UI options. But the slow and clumsy UI will not change that much I fear.
Someone once wrote here that Prime's UI is like having to type with boxing gloves on - I don't see that this will change significantly.