Twitter has the advantage of huge entrenchment of many communities for a lot of use cases, and a lack of good competitors. I do not believe that a decentralized alternative is likely to take their place.
The fact it's decentralized isn't the issue. Everything is decentralized if you look close enough. It's jure pure network effects. Twitter has like 20 competitors right now and none of them is outshining the rest, including Mastodon. This confuses people and makes them stay at Twitter.
If there was JUST Mastodon, and one decent client for each platform... well... there wouldn't be Twitter anymore.