Some of them for sure! It's so much easier for me personally to just tell the currently-preferred-LLM-model or agent to do something for me instead of dealing with apps and dashboards!

Some will, some won't. I prefer some webapps to their native ones and vice versa. I used to run some proprietary apps that I replaced with open source ones, often clients interfacing with already self hosted stuff. I rarely touch Kagi anymore because my own hosted model + searxng drops results faster. I don't expect most of these apps to go away just because of agents/assistants alone.

Proprietary apps and services will probably go into protectionism and will shed users in doing so.

Custom launchers and widgets will likely be replaced by user instruction-driven processes at some point.

I think a chatbot or voice is a horrible interface for most things. There is 0 chance for discoverability, so the application's function is limited by the user's imagination. Most people aren't going to think about the various things a program could solve for them. Even with a UI, most users only use a small fraction of the available options. Without some visual cue to let them know features exist, I'd bet that most users would use even less.

My day job is automation stuff within a large organization. Most people, even within a technical organization, don't seem to think about how the computer can solve problems for them. The other day I used Claude to turn a massive csv dump of data into a dashboard to see trends over time. I don't see other people doing that.. but if Excel had a button for it, I'm sure they would do it.