The Studio doesn't update the Bonita version in the pom automatically because we can't assure that there is no breaking changes on our transitive dependencies.
You can use the range syntax as suggested by Laurent if you don't want ot update in manually, but keep in mind that eclipse will try to resolve all the dependencies in the range, it can lead to performance issues.
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.