What are your future plans when it comes to smartphones?

Same as my current plans: I pick a smartphone that runs a privacy-friendly OS, and only use privacy-friendly apps.

Right now, that's a de-googled Android phone running LineageOS, with F-Droid as the only app store. In future, it might be something else, like a non-Android Linux phone. My current model is 6+ years old, still gets OS updates, and still works great, so I imagine the open-source options will have improved by the time I need to replace it.

I care about things like data exfiltration, battery life, cost, and hardware longevity (important for minimising e-waste). I don't care about AI unless it happens to impact one of those things, but since there's nothing inherent to AI that does, the issue of whether a phone has AI capabilities is irrelevant.

By not using these AI features, you pay a lot for features you won’t be using.

Only if you're an early adopter. Like all new tech, further research and production volume will make it relatively cheap.