Dropping IE9 support or other older browsers

Created by: pattonwebz

Recent days have shown that maintainers and some developers are in favour of dropping IE9 (and maybe even IE10). Can we please reopen that discussion? I don't think that this decision can be explored fully in the space of 24-48 hours, especially when it's the week before Xmas and many people are not around to weigh in with their opinion.

This issue and PR are both under 48 hours old and both are locked without allowing everyone who is following V4 development the time and opportunity to say what they think.

https://github.com/twbs/bootstrap/issues/21387 https://github.com/twbs/bootstrap/pull/21389

If anyone has an opinion to share, or any data to support their decision, please share so that the decision to drop support can be explored fully to reach the best outcome for developers and end-users.

Thanks in advance for any input you have :)