I am not leaning towards this idea either.
Sure, it would be useful, but I've found in some of my projects the cluttered cluster of functions that are not currently collapsible may have been beneficial; they drove me to organize things in classes and libraries, which IMO organize things even better.
I also like the simplicity of the IDE, leaning me further from the regions idea. I sort of like having only 2 areas of text (code section and message box thing for errors and stuff), 3 scroll bars, a row of tabs, and 6 or 7 buttons in the window.
I agree that arduino MUST NOT become like Microsoft word...*shudder*