Editors are replicating terminal multiplexer functionalities - tabs, windows, and now with terminal emulation they have become terminal multiplexers. Terminal multiplexers are also replicating editor features (copy-mode of tmux, for example). Unfortunatly neither has reached a state to completely supersede the other - I always find vim's window-manipulating commands obscure, and copy-pasting with tmux is never as satisfactory as in vim. I suspect that such a state will never be reached, since both party are still keeping their narrow mindsets - vim still tries to remain an editor, and tmux still tries to remain a terminal multiplexer.
The world can benefit from something that is built as both an editor and a terminal multiplexer from the very beginning. There is acme (http://en.wikipedia.org/wiki/Acme_%28text_editor%29), but we need something slightly more elaborate and friendlier to the keyboard.
(There is also emacs, which is both an editor and a terminal multiplexer. But it is also a news reader, a web browser, and a million other things. Something that is "just" both an editor and a terminal multiplexer is probably better for the reset of us.)