I fear if Emacs was remade with graphics at the forefront and text as a secondary concern, we'd lose a lot of interoperability this "text program" thinking brings to the table. Being able to work with an UI in a way you would with text files - jumping, copy-pasting, editing the UI itself, all with the exact same shortcuts and conveniences you use for programming - is incredibly powerful and something not really replicated elsewhere. I mean, number one complaint against TUIs and GUIs is that the data is locked inside, and you can't easily take it out and send elsewhere. With Emacs UIs, it's not true - if need be, you can select, copy and paste the whole thing, UI included, and it looks good in a text file and can be operated on programmatically.
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Further improving performance of elisp and enabling true multithreading/async: that would be a huge breath of fresh air in Emacs.