Yeah, I mean it's not like they need to allow air to pass to the interior of the phone. All you need is a couple of exposed metal tabs, no different than the USB/lightning port.

Exactly, I think there are solutions for more or less everything I listed, or solutions could be found if necessary.

I think the headphone jack is a very practical component of the phone, and miss it regularly, but removing it does remove a few limitations on the designer.

At some point, in perhaps the not too distant future, I wouldn't be surprised if phones had been reduced down to look like not much more than a piece of glass. Maybe even a piece of flexible glass!

That's definitely been the trend for a while now, and things like edge to edge screens and wireless charging move us further in that direction. Thankfully neither of those seem to have necessitated the removal of some other function. There have been other casualties other on this path to simplification, such as the removal of the physical home button, but I don't think any which leave as big a gap as the headphone jack.

That would definitely be cool, we see them fairly often in modern scifi films/shows too nowadays.