@Natanox I highly doubt the same end result will happen here, but rather, the scientific law of osmosis applies here; the bigger platform loses users and the bigger platform gains users.
#Gab is a great example of this, they joined the #Fediverse when they had 1 million users and the #Fediverse had 3, and lost so many users (including myself!) that many of them formed #Fediverse instances that went on to become the biggest instances on the #Pleroma side of the #Fediverse.
I mean, how many people on the #Fediverse do you really think will join a platform run by #Meta? I would think there would be much excitement about the opportunity to convince millions of #Meta users to join a #FOSS platform.