I've been working on an open source ZTNA project/product https://github.com/octelium/octelium for many years and I am actually very open to the idea. Machine learning has already been in use for years when it comes to anomaly detection. Maybe modern LLMs can be used to automate access control, partially or fully at enterprise scale in the future. The idea is to have a policy engine that's controlled by AI that uses a mix of long-term semi-static info such as group memberships and permission boundaries, short-term info such as behavior (e.g. access logs) and current session's authentication strength level (AAL) such as FIDO as well as near real-time external information (e.g. IdP, SIEM, threat intelligence, on-call management) to dynamically adjust users' access control to build up some sort of a context for each user and each session that can increase or decrease permissions without having to manually add policy rules or going through request/approval flows, while optimizing for the main objective (i.e. minimizing access grants for every subject to any resource under whatever context unless when it's necessary). This can be unified for both humans and non-human identities, including agents.
Good, realistic take. There's a lot of context that can be drawn on to make better decisions and look for weird.
And then agents come along and some people want their agent to be able to do anything they can do with zero friction. That usually lasts until the first time something goes wrong ;)