Instead of having a human interact with your UI, in the future, it’ll be an AI agent using your UI on behalf of its human. At the limit, human users will vanish from the web and many software applications.
A likely scenario is that the “user” only interacts with his or her agent, and the agent then performs any specific interactions with the services needed to accomplish the tasks the agent was ordered to perform.
AI is the new UI because it fundamentally changes how we interact with technology.