I rarely use Siri - basically I've gotten used to it being unhelpful generally, as if I ask it something even slightly complex, it gives me a "this is what I found on the web" list. Yuk
But - I do use it occasionally in the car, via CarPlay, really only to read out messages, dictate responses and call people. For which I think it's actually really good.
So what I think we'll end up with, is a "local assistant" - like Siri now, that works on your phone without going to the cloud. But also something akin to ChatGPT et al which can respond to random questions (via the cloud).
Apple might combine these, but they are very keen to push their privacy credentials, which would be easier if they were separate.
I do agree with the majority of comments; Siri is just not very powerful. Interacting with ChatGPT is interesting as it basically has a reply for every question - of course with the caveat that some responses are not factually correct! Whereas I would never consider experimenting this way with Siri, it'd just keep giving me lists of websites.
Based on their recent brandings, I'm going to bet it's called: Siri+ or maybe SiriPro (but you still activate it with "Siri").