Upon the Twitter response it looks like he have made plans of more features getting added to Twitter. It looks like he have planned something that could provide access to anything around through a single application. Maybe he's planning to take the position of Google as people reach it for every needs 
Yeah im guessing hes going for a decentralized internet browser, youtube alternative, gmail alternative, and social media. Of course, big quantitation marks would need to be put between decentralized since attempts at this have been pretty lame, see the steemit clusterfuck and other derivatives. If it needs it's own token, it will need to prove the game theory cannot be gamed as seen before. I don't see how Bitcoin fits in all of this beside implementing Lightning Network payments natively, that would be cool, however the Bitcoin blockchain is for Bitcoin transactions, not some Elon Musk experiment.