Yes, fortunately, this is being picked up by more and more distributions, so at least new installations will have this.
At the same time, NTPsec shipped with Debian (and probably Ubuntu as well) uses all four numbered zones, with only a tos maxclock 11 stance limiting the number of servers solicited. So somewhat biased against IPv6.
Same for the standard BusyBox-based sysntpd on OpenWrt, which I believe is also picked up by the ntpd classic package, and the ntpdate package derived from the ntpd classic sources. The latter has all four numbered vendor zones as fallback, while chronyd on the other hand comes with its own IPv6-enabled default configuration.
Tasmota is using IPv6-enabled zones as default. Which is interesting as only a subset of devices has support for IPv6 enabled in default builds. Interesting as well that they don’t seem to have a vendor zone (see last paragraph below). And they don’t only use the global zone, but additionally the 2.europe.pool.ntp.org and 2.nl.pool.ntp.org continent/country zones, I guess to ensure the devices get time wherever they are in the world, even in severely underserved or somewhat broken country zones.
Would be interesting to see what systems coming with systemd-timesyncd use by default, probably depends on the distribution and how they customize this. I currently don’t have such a system at hand I could quickly check for this (replacing timesyncd typically is one of the very first things I do on a new system, will check next time this comes up).
Anyone installing OpenNTPD from the Debian repositories probably is getting pool.ntp.org by default (seems the package hasn’t been updated in quite a while, though…).
Default in ntpd-rs seems to be the un-numbered vendor zone as well, though they at least mention which numbered generic, i.e., non-vendor pool zone to use for getting IPv6 servers as well (though misleadingly mentioning this with reference to IPv6-only machines only), as the vendor zone does not support IPv6 at all (see next paragraph).
And new vendor zones, if one can be obtained at all, apparently are IPv4-only by default, and it seems somewhat difficult to get IPv6 added later on even on request. So if vendors take the vendor zone topic seriously, potentially a lot of new devices/software installations will be IPv4 only.