The answer depends on whether you wish to conserve runtime data. For instance if you have a Bonita platform (Execution Engine and Portal) set up with running and archived process instances that you do not want to loose then migrating your platform is mandatory.
However, if you do not have such an environment or if keeping these data does not matter you can just discard the Platform and install a new one with a more recent version.
Now for development resources (process diagrams, forms, connectors…), these can just be imported in a more recent Studio. The migration process is automated.
Bonitasoft empowers development teams with Bonita, the open-source and extensible platform to solve the most demanding process automation use cases. The Bonita platform accelerates delivery of complex applications with clear separation between capabilities for visual programming and for coding. Bonita integrates with existing solutions, orchestrates heterogeneous systems, and provides deep visibility into processes across the organization.