Not yet, sorry! RTL was our big feature addition that came with some significant departures. Tried to keep the breaking changes and overhauls to a minimum compared to the v3-v4 migration.
Yup, and we're looking at dropping Legacy Edge from our supported browsers for this reason as well. As of right now, we still have v17 and v18 in there, but there's a PR open to remove.
Who knows how long this will take with the pandemic (and I work full-time at GitHub, and most of the team has full-time jobs), so all that does slow us down. That said, this should be faster than v4's development, and with fewer and smaller breaking changes by comparison.
I wouldn't start getting into the weeds with it in any kind of production environment until the beta though honestly. Release date for stable v5 is hopefully months away.
With how the web has evolved over the years, we've been caught on the side of being too far behind and being too far ahead. We want to move faster and find the right balance. v4 was a bit of a nightmare scenario, and upgrading from v3 was nuts. v4 to v5 _should_ be much simpler by comparison. Still some breaking changes, but nothing like before.
And yes! Definitely something that you can theoretically run forever without issue. Browsers basically have to keep supporting the historical properties, quirks, etc, so once you've built it, you're largely good to go :).
Nope! We're a small distributed team that works on Bootstrap when we can. Jacob and I created it at Twitter, but we took it with us in 2012 when we both left :).
Reinventing the wheel is awesome! More people, myself included, need to build from scratch and learn ourselves every now and then. Definitely interested in more tooling around helping folks getting started, too. Spent a lot of time on the customizing side for this release.
Unsure how we'll tackle this overall, but we are looking at increased customization and variants for a handful of key components. This might be a mistake, and if so, we'll hope to hear it in the alphas so we can shift gears and do dark mode across the framework. That said, it could be too far reaching and mean it'd come in v6.
Speaking to the lifetime of each major version—Bootstrap 4 can't go into any kind of LTS situation until v5 is fully stable. That's going to take a few months just being honest, so I fully expect v4 to be around into 2021.
We've also maintained security patches and more for v3 where appropriate well past the LTS for the web's sake. While we try to have guidelines around it, we want to help move things forward for the web :).