Twitter doesn't release stats on what the most popular feature requests are, but it's pretty safe to say that an edit button is one of the most top requested features for the social network. In fact, "Tweets but editable" is a running joke, and has been for years now. After going so long without any kind of promise of an edit button, this probably shouldn't come as a surprise, but it's not happening.
In a video with WIRED, CEO and co-founder Jack Dorsey answered the question from @taisydorres. He later responded to the tweet from an account that's associated with the video.
No. We’ve made some practical considerations, but we’ll probably never do it.— Jack Dorsey Tech Support (@DorseySupportsy) January 15, 2020
The answer to the question in the video was, "No." Dorsey explained that in the beginning, it was because Twitter was based on SMS messages, and SMS messages can't be edited. While the initial goal was to preserve that spirit, now there's a different set of challenges. For example, if you tweet something and it gets retweeted thousands of times, you'd then be able to edit that tweet for everyone that's already shared it. Dorsey says that Twitter could give you a one-minute window to edit, but then you'd have to wait a minute for that tweet to be sent, because once it's sent, it can be seen, citing the same concerns.
Of course, Dorsey didn't address the fact that most other social networks - such as its biggest competitor, Facebook - allow you to not only share other users' content, but also edit it. If other social networks can work through these issues, surely Twitter can as well.
Either way, Dorsey said that the edit button definitely isn't coming this year, and probably won't ever happen.