Yes, but there's a caveat. Neither CF nor Cobol ever held the place of PHP in either popularity or as a bar of entry in development. PHP is - meaning that as long as there's some jobs to had PHP will be the land of fresh competition from newcomers. COBOL's high was brief and nobody ever said that Cobol provided an easy induction into development like PHP (same for CF).

The other thing is that PHP's longevity has surpassed many and due to its active development and rate of change there are already many versions in the wild but their footprint keeps shrinking. I guess there's the potential that any of PHP 4/5/7 may remain a niche, but the threshold is slowly moving upwards.