Mobile developers are ironically stable, being forced to use the language of their platform and maybe whatever their companies cross platform layer is made out of. I've been doing ios dev for 4 to 5 years and it's only whatever is new for the new OS version in objective-c. I was paid to learn all the newness of ios 7 as I transitioned the app towards it. Swift is mostly objective-C in a new skin with welcome improvements, so learning it is easy.
Note: "If you don't meet all those criteria, apply anyway. We'd love to talk to as many people as we can."
My local craigslist has dozens of jobs posted today looking for "Linux sysadmin" with scant requirements, offering $60-70k. Not huge money but better than being unemployed.
I keep wondering if the only reason you see that many ads for a trending tech is because those are newly-founded startups or small web dev shops that will be going under in a year anyway, or maybe because tech recruiters are out of ideas.
In every other place in the world nobody give a damn about the latest technology. They only need something that work for they problems.