TAI currently differs from UTC by 35 seconds, so if you literally switched to it, every clock in the world would jump 35 seconds. If leap seconds are abolished, UTC and TAI will remain 35 seconds apart forever.
And then that time will be neither UTC not TAI. Either we'll have to call it something different (like GPS time: always offset from TAI by certain number of seconds), or a different name will have to be made for what used to be called UTC (time tied to earth rotations, from which zoned wall time is to be delivered). Great. That's exactly what https://xkcd.com/927/ is about.
I don't know if that's true. We already have a name for the time that is tied to Earth rotation, "UT1". Users who care about positions of astronomical objects can refer to that. UTC was always a bit of a compromise, which partly tracked UT1, but only up to the nearest second.
On the other hand, I think the idea of abolishing leap seconds is to no longer derive wall time from earth rotation, and to derive it from atomic time instead. So "UTC" would still refer to "the source of wall time". As I understand it, this is the point of changing the derivation of UTC: there are lots of laws in different countries that say that wall clock time is tied to UTC, so if we want to switch from earth rotation to atomic time, it is easier to change the definition of UTC than to change the laws in all those countries.
