I’m fairly confident executable text as well the other functionality of current smalltalk systems can be implemented within a modern IDE framework. What needs updating are the UI components, views, layout, etc. For example, I can envision a left hand tree component for the display of packages/classes/protocols/methods the same way it’s done for for almost every other language.
Could the modern IDE paradigm be approximated within current Smalltalks? Probably, but pulling that off in Squeak or Pharo seems like the wrong approach. Also, deployment of server side applications is more cumbersome in Squeak or Pharo than with GNU Smalltalk.