COBOL was developed in the 1950s
Not "the 1950s". The committee to design it was started in April 1959, the initial specification was published in January 1960, and the first two implementations were able to run a standard example program in August and December 1960. Widespread adoption was some time later.
Let's be generous and use 1960 as the date. That's 60 years ago.
the fact that it is still in use and there is still demand for COBOL programmers says something I think. I've never played with it myself but obviously it gets the job done.
COBOL was designed to represent the problem domain, not to reflect or be influenced by current computer technology at the time, even if that meant it was inefficient. This is a good thing for longevity.
Does anyone think Javascript or Swift will be in common use 70 years from now?
JavaScript was designed and deployed to millions of users within a few weeks in 1995. That's already 25 years ago, so it's only got 35 years to go to match COBOL today.
Yes, I hate the idea, but I'm sure JavaScript will still be supported in every web browser in 35 years from now, and used by huge numbers of web pages.
C is from 1972, which makes it 48 years old. I'm absolutely confident it will be still in wide use in another 12 years.
Swift is a tougher proposition. It has a lot of competition as a high performance applications programming language (replacement for C/C++) from Go, Rust, D, C#, Java, Kotlin. Swift is a bit more advanced and powerful than most of those, having taken a lot of influence from the ML, CAML etc school. Apple has invested a huge amount in it since 2010 (public release in 2014), the compiler and libraries are extremely mature and optimised, it is open-sourced and available on Linux and IBM's mainframe z/OS (as a competitor to COBOL). I don't think Apple will switch to anything else any time soon, which makes it a major language for as long as the world's largest and most profitable company stays in business and important. Will that be 50 or 55 more years? I don't know. That's a long time. I'd be very surprised if it's less than 20 or 30 years though. Learning Swift is one goal of my current funemployment on the list I made a month ago :-) (along with FPGAs, Webasm, and Go)