I’ve written code myself that depends on regex patterns (4 digits followed by one or two letters) to match timezone version numbers, so I definitely would not want to see the version formatting change, at least not abruptly and without plenty of lead time before the first version numbers in any new or modified format appear.

Specifically, this is what is documented and this is what our software supports:

...

Since 1996, each version has been a four-digit year followed by lower-case letter (a through z, then za through zz, then zza through zzz, and so on)

Deborah