Two are listed below, but there are many more. Nicky case is one of the most well known ones, Bret Victor himself is very well known and very active. There're also a lot of lesser known people in the space,
- Patrick Dubroy: wrote Ohm, makes cool stuff
- @azlenelza on Twitter
- @codexeditor on Twitter: He's building by far the most professional, serious and very very inventive digitised text... system? I have no idea what to call it. It's far far beyond what Roam, Obsidian etc can do. I think Ted would love to have a conversation with this guy. It goes deep in all directions.
- Andy Matuschak is worth mentioning. Goes deep into learning and memory research, and building tools around this.
- Tudor Girba @girba on twitter, makes moldable software environments: Tl;dr, tools to make custom IDEs in seconds to minutes that fit your current task perfectly. Very interesting stuff built on Pharo smalltalk
- Omar @rsnous on Twitter, posts thought experiments about weird interactions with computers multiple times per week. Sometimes cool ideas come out of it :
Of course not all of these people are or will be visionaries of the same level as Ted, but these are all people working to experiment with the status quo, or step out of it completely.