I am also mindful that simply leaving is only one part of the puzzle.
If I was sitting on a huge pile of Twitter related code with a full set of Twitter related reading/posting functionality, I think I’d head toward some of the new open protocols coming out of the IndieWeb to build a new user base. By supporting feeds like RSS, ATOM, JSON feed, and even h-feed (possibly via Microsub) for the feed reader portion and building in the open Micropub spec, one could rejuvenate old Twitter apps to work with a myriad of microblog-like (and even traditional blog) functionality on platforms like WordPress, Drupal, Craft, WithKnown, Jekyll, Kirby, Hugo, micro.blog, and a myriad of others in the future. Suddenly all those old Twitter apps could rise from the ashes and invigorate a new, more open community. Given the open “architecture” of the community, it would give developers much more direct control of both their software and futures than Twitter has ever given them as well as a deeper sense of impact while simultaneously eating a nice portion of Twitter’s lunch. With less than a week’s worth of work, I suspect that many of these old apps could have new and more fruitful lives than the scraps they were getting before.