The initial version was deployed to Wikidata in May 2018.
With the WikibaseLexeme extension largely stabilized time has come to implement support for it in Pywikibot.
In addition to three classes for Lexemes, Forms and Senses (see the data model) there should probably be a new site class which implements them.
The design for these should probably be done in conjuncture with T223820: Properly implement structured data access on Commons in Pywikibot and T186200: Rewrite Wikibase data model implementation