The assertion that an ecosystem with close to 500m users now and over 800m in a few years will not be viable because there’s another that’s bigger seems pretty simplistic. It can’t be taken for granted that any ‘winner takes all’ dynamics will work like that.
Particularly when there’s more money poured into the one with a smaller share.
Not that this will stop this argument from being promulgated. Whether that’s because the people who keep making it can’t read or simply choose not to understand this remains unclear.