From the Forecast page I know that the Realtime Game Editor development is on hold, but there are other tools in External Tools as well.

I'd like to is there any overlap features in those tools? or a unify tools?

For instance, there is terrain editor in MED, WED, Realtime Game Editor, External tools.....too overlap I think.

Why not create an ultimate editor include model, level block, terrain, source code, shader, panel?

You mean something like an IDE?
Just start one application (GameStudio IDE) and have all editors inside of it?

If yes: I would also like that!

The external tools are meant as plugins to MED and WED. The "ultimate editor" is WED that serves as IDE.