Around here (Finland, neighbouring Norway), the average car on the road is 12 years old, so if we start to get DAB radios now, almost half of them will have it by 2025.

Many more cars have right now Bluetooth connectivity in the audio system, so it'll be streaming from the phone then.

An aftermarket head unit with DAB+ costs about €150 with installation. Owners of older cars aren't stuck, but they will have to pay for the privilege of continuing to receive radio broadcasts.

Will that integrate into the car electronics, and be able to run e.g. the satnav UI if that is included in the previous one?

This is just another example of satnav being a terrible option to build into cars. Who wants to use a "custom" nav system kludged together by the lowest bidder ten years ago when we have much better on our phones?

Well, someone who doesn't want to reveal his/her driving habits to Google, NSA et al?

Good point, but one probably does that as soon as one purchases a smartphone...

DAB service in the UK is a significantly better experience than FM when driving.

However, receivers vary wildly.

I rent cars frequently and while all new cars have DAB, the quality of implementation is not consistent.

There's a huge difference between the crappy ones that constantly drop the signal and the good ones that almost never do, even in really remote (and hilly) areas.