Since 2020, ITIL v4 has been the official successor to ITIL v3, although this does not mean that the third version of the IT guide is no longer relevant. This is particularly due to the fact a lot of the content in ITIL v3 can also be found in ITIL v4.
Thus, the practices of the new edition are strongly oriented towards the processes described in the predecessors. The service lifecycle approach also continues to play a role, although it has been removed as a key principle: The Service Value Chain, which is one of the five components of the Service Value System (SVS) from ITIL v4, is more or less an extension of the ITIL v3 lifecycle.
However, the fact that ITIL v3 continues to be valid is due in particular to another reason, which the authors of the current edition have emphasized from the beginning. It's because many IT companies still need clearly structured processes such as those described in ITIL v3. Agile structures, which are the aim of ITIL v4, are becoming increasingly important in principle, but they often do not (yet) fit into everyday business life.