Not to mention, when was the last time Facebook successfully launched a new standalone social app? Remember Poke, their Snapchat clone? If you do you’re in an exclusive club. They had to pivot the entire Instagram app in order to compete with Snapchat and Twitter isn’t a big enough threat to ever justify doing that. I think it'll get merged into a "text" type of Instagram post eventually and otherwise killed off.
Side note, but:
> There's massive pent-up demand for an alternative
I actually don't think there is. Twitter always had a relatively low number of users compared to other networks. The key (and what Zuckerberg covets) is the cachet of it being where journalists and celebrities break news.