You could put the "new" mode of operation directly against the "traditional" one only if you were proposing an actually new paradigm (like the point-and-click interface). And even then you would still want to allow a way to fall back to what's tried and true.
As TK is essentially an _improved terminal_, I don't see a reason to totally break off from the current power of the traditional CLI, especially if alienating current power users in the process.
The biggest limitation are the existing applications. Initially the new features could be opt-in, and as the new idea picks up, you would then have more and more console applications support the new type of terminal.