Ask HN: What happens to old IoT devices when 2G network is discontinued?

I'm based in Switzerland and I have many IOT devices that I've been using since many years.

All my devices are only 2G compatible some have a Swisscom network sim and other a Sunrise network sim. Swisscom will stop it's network end of 2020 while Sunrise end of 2021.

It's quite difficult to find answer to some of my questions online if anyone could help out it would hugely appreciated.

My main question is :

- Will Swisscom 2G sim roam to the Sunrise 2G network once Swisscom 2G network has been stopped ?

Then I had some more questions I was asking myself

- What happens when your provider stop his 2G network?

- Is there any backup plan for all the IOT devices out there still connected to the 2G network ?

- Or roam to other adjacent countries 2G network ?

Thanks in advance.