Probably not become lightning connectors...

The headphone jack was already destined to be replaced by USB type-c on many (not all) portable devices. Apple's move may change the time line, but does not change this fact.

While my laptop doesn't have a floppy drive anymore. It does have a DVD drive and USB ports. Who is this 'everyone'?

"ports older than USB" meant serial and, later, ethernet.

My new-issue Dell work laptop lacks an optical drive and Ethernet. My dad just bought an even beefier Dell laptop and the first thing he asked was "where's the DVD drive?" Dell offered to send him a free external USB optical drive, but told him that internal optical drives were simply not an option on that make of laptop.

Did Apple ever offer a laptop with a serial port?

Every Apple laptop prior to the Powerbook G3 Lombard, released in 1998, had serial port(s).

Yes, in the form of ADB at least.

Nothing.

The question is, who is going to win: the legion of teenagers and young adults who listen to audio via the headphone jack, or device makers?

(It's the legion.)

If you had a replacement that was better - cheaper, less of an annoyance than $5 headphones plugged into a cheap phone - then you might win. But the proposed replacement is superexpensive, battery-powered wireless headphones. When the no-strain-relief Apple cables break, probably within weeks, you're supposed to buy another superexpensive set. That's not going anywhere with the horde of teenagers. It's a non-starter.

I would happily buy a phone with two type c ports which could detect and use analog headphones using pins on the type c plug for their analog signal.

Some Android phones will have 3.5mm jacks, and some won't. At least there will be choice.