- Switching to single-major-version release numbering. The number of people who say "PostgreSQL 9.x" is amazing; even *packagers* get this wrong and produce "postgresql-9" packages. Witness Amazon Linux's awful PostgreSQL packages for example. Going to PostgreSQL 10.0, 11.0, 12.0, etc with a typical major/minor scheme might be worth considering.
In this case you don't even need the 2nd digit...
Btw, -1 for the idea, as it would remove the possibility to tell that a new major release incrementing the 1st digit of version number brings more enhancement than normal major releases incrementing the 1st digit. This was the case for 9.0, helping people in remembering that streaming replication has been introduced from 9.x series.
