Dunno if they'll become ubiquitous, but I think various foldable forms will at least stick around as a viable market segment. Most early-ish adopters I know from the zFold and zFlip 3 generation are planning to get another when it's time to upgrade. Granted that's a biased sample of like 5% of the people I know IRL, but still it's not too common to see that much agreement after a year+ of use for a product that's just a gimmick.
I'm not sure whether foldable phones will become what everyone uses, but this is typical for new products that have not started zipping up the S curve.