If this could ever happen, there will be no point in GUI apps anymore, your AI assistant or what have you will just interact with everything on your behalf and/or present you with some kind of master interface for everything.
I don't see a bunch of small agents in the future, instead just one per device or user. Maybe there will be a fleeting moment for GUI/local apps to tie into some local, OS LLM library (or some kind of WebLLM spec) to leverage this local agent in your app.