Wouldn't it be better for it to become an actual standard before using the new variants? If something changes between now and when it gets standardized, you'd have to deal with the difference going forward.
The ULID spec has been stable for many years now and changes are extremely unlikely. The spec wasn't designed for forwards compatibility for future specs, which on the one hand makes it a possible risk if there are future specs, but also gives some weight to the "promise" that future specs are not expected and will be backwards incompatible anyway.
It would be nice to see ULID recognized by some standards body that isn't just "itself", but also unlike UUID version changes doesn't need to be. The new UUID versions need to be backward and forward compatible with existing standards documents "universally", whereas ULID is designed to be entirely self-contained.