What would be the advantages of dropping IE10?

Thinking aloud, probably just relevant for post-4.0 (right, @mdo?):

• #23770 could be reverted, possibly improving JS minimization and be a micro-optimization for undefined checks
• Notes about missing pointer-events (as added in e.g. #23826) could be removed.
• The pointer-events workaround for #23222 might be worth checking out again.
• SVG images fix not needed any more (#23476)
• Some of the notes about disabled <a> buttons could be possibly removed
• #22493?
• Doing flex-basis: 100% instead of flex-grow: 1 might not be needed any more (#23652).
• No need for -ms- prefix for flexbox properties (as noted by @alecpl, thanks!), dropping -ms- prefix for touch-action

Can I use comparison: http://caniuse.com/#compare=ie+10,ie+11 IMHO, most noteworthy from there:

• pointer-events
• hidden attribute
• const and let (not whole ES6 though, no idea whether Babel can make use of this)

Some other possibly relevant things:

• Various touch improvements, sadly most of them have to do with the pointer events API, but also various touch related (but mostly IE/Edge specific) CSS properties:
  • https://msdn.microsoft.com/library/bg182636.aspx
  • https://blogs.msdn.microsoft.com/ie/2013/07/31/ie11-touch-browsing-for-todays-web-and-beyond/
  • https://blogs.msdn.microsoft.com/ie/2013/10/22/enabling-new-interoperable-panning-experiences-through-the-css-scrolling-snap-points-specification/

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(Concerning desktop browser usage, it is below the 0.27% of IE8 and 0.29% of IE9 according to http://gs.statcounter.com/browser-version-partially-combined-market-share/desktop/worldwide/#monthly-201811-201811-bar, with no significant numbers in any continent. It’s also considered unsupported by Microsoft on any desktop end-user operating system, see https://support.microsoft.com/help/17454, under “What is the Lifecycle Policy for Internet Explorer?”; Other UI libs which don’t support IE10: [1], [2], [3], [4])

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Dump

• #25587

[dvmuccillo]

IE11 isn’t recommended anymore by microsoft itself.

Can’t we afford the price and remove its support? When v5 release come maybe someone will still be developing to support a software marked as dead or that will touch a very old app and try to upgrade it.

But aren’t there no more positive points than cons as to the removal of the support?

[XhmikosR]

BTW I agree with @coliff’s answer. That being said, I’m not sure what the verdict will be for v5. Because dropping IE11 makes JS cleaner. We could suggest a specific snippet for any needed polyfills from https://polyfill.io/ thus making the transition smoother. CSS is another issue, but we’ll need to assess that when time comes.