If he really wants to do that, by buying Twitter he removed the incumbent and also acquired its users. Much easier than competing and trying to make people switch to a new service.
My unverifiable prediction: no matter how many users will leave Twitter, the ones left will be more than the ones that would be using a new service after 1, 2, 5 years.
Well, not often, no. I'm not really expecting that to happen with Twitter, I just think it IS a possibility. How many websites/apps that were as big as Twitter have totally disappeared?
I'd argue neither was anywhere near as big as twitter. In terms of users, maybe — I have no idea. But in terms of reach and influence? I don't think so.
I think regardless numbers, it is usually a slow burn for situations like these. And probably plenty of people will probably not see a space to fill and try their luck. Hopefully, one of them will work.
My unverifiable prediction: no matter how many users will leave Twitter, the ones left will be more than the ones that would be using a new service after 1, 2, 5 years.