Imagine your agent will stop wasting tokens using grep to find symbol usages if he can just ask IDE where it is used. They are not the best option for vibecoders right now but who knows what will happen in 1 year.

Can't agents just use a language server? There are already a bunch of projects that provide this, e.g.: https://www.agent-lsp.com/

Doesn't seem like a huge differentiator anymore?

I don't really know much about their current users, but from a business perspective, post-tokenmaxxing and them having an IDE, it seems like the most efficient environment for having a human in the loop is something they could tackle?

Well nobody needs to use IDE. There were always people who used vim with tmux as their IDE. The value of IDE is the I as in integrated - I see some value in having easy to manage single dev environment with batteries included. (I'm not an IDE guy though, and I personally closer to vim/vscode + plugins)