I'd love to see more editors/IDEs that operate at a higher semantic level than plain text. The biggest problem is of course interoperating with existing language/development ecosystems. I have pondered in the past about a language or platform where everything is stored internally as some form of AST, and text is just one of the possible representations. It would at least solve the coding-style (well, the formatting part at anyway) issue for once and for all; everyone just maintains their own CSS/XSLT-alike transforms with tabs or spaces and brackets and semicolons wherever they like.
I've come across occasional research projects in 'structural editors' which only allow semantically correct input (and, depending on the size of the input alphabet, can function through almost 100% autocomplete menu input)
Anastasia[1] is one that I know of, and this Modeless Structure Editing by Sufrin et al.[2] looks interesting.
The main issue I can see, apart from the effort involved, is how to deal with incomplete documents, since almost by creation or editing process will have interim invalid structures. Emacs paredit can be pretty infuriating if you don't use its specialised operations and try to edit your code in a way that malforms the structure.