Since version 3, TeX has used an idiosyncratic version numbering system, where updates have been indicated by adding an extra digit at the end of the decimal, so that the version number asymptotically approaches π. This is a reflection of the fact that TeX is now very stable, and only minor updates are anticipated. The current version of TeX is 3.141592653
Knuth has also decided that once he dies, a last version will be made which sets the version number exactly to pi.
He’s gonna live a long life. Until we know pi.
He has to finish section 7.2.2 of his book