The RC of IFC 4.3 is available at:
https://technical.buildingsmart.org/standards/ifc/ifc-schema-specifications/
Would be great to try out the RC already if possible with read and write with FME. Not sure how IFC is implemented vs XML. However with XML you can fairly easy point to an xsd and get a new xml standard within FME. I guess its not as easy to do the same for IFC + XSD ?
Mostly using this towards roads, railway and bridges
Changes here: https://technical.buildingsmart.org/standards/ifc/ifc-schema-specifications/ifc-release-notes/