Nothing will stop, there are tons of companies willing to get into this alliance and be a part of Libra. Wait for several more months and you will see that empty places will be booked by same size companies or even bigger.
This is unlikely to happen. The Libra project, if released, is unlikely to reach half of the popularity and relevance for which it was designed. With the advent of national stable coins of various states, such as the USA, China, India, which have already announced their release, it is unlikely that many will still prefer to use Libra. Zuckerbergs authority in comparison with the authority of the leading world states does not lend itself to any comparison.