Elcaset would be equivalent to a quarter-track 3 3/4 ips machine. We have a few of those around and they sound pretty good, especially the Akai with a crossfield head design that makes 3 3/4 sound like 7 1/2.
Elcaset would have been a pretty fine release format, IMO. More pleasant than CD, cleaner than vinyl, smaller than VHS, and more durable than any of them. 1/4" tape doesn't really wear out unless it's abused.
I was telling the previous station manager of my disdain for all forms of digital technology, and he offered digital watches as a counter-example. I said, "Actually, I have three or four digital clocks and NONE of them keep accurate time. If digital watches had never been invented, and all the R&D went into mechanical watches instead, we'd probably have cheap and reliable mechanical watches by now."
Short of supervillain tactics (like designing a virus that eats rare earth elements and disables all the world's digital devices), it'll never happen. But one can always dream.