I recently asked Firely about their plans for supporting the coming FHIR R4B and FHIR R5. Here's what they say.
Our tools are well on our way to prepare for the releases of R4B and R5. The previews of these FHIR versions are already available in our .NET SDK, Firely Terminal, Forge and Simplifier. We have built an alpha release of a migration tool to migrate users' resources from FHIR R4 to R4B. You can try this out by opening R4 resources in Forge R4B. Forge will automatically migrate anything that it can and inform the user of any changes that are still required by the user. Feel free to try this out, we welcome any feedback.
Other news from New Zealand FHIR Registry
See it here https://registry.fhir.org/package/hl7.fhir.uv.ips|1.1.0 or here http://hl7.org/fhir/uv/ips/STU1.1/
And we've copied the package into our NZIPS project as the starting point for our own derivative
HL7NZ has just published the second version of the HL7 FHIR® NZ Base Implementation Guide
Firely has published an e-book on the experiences of NHS Digital, HL7 Germany and other Simplifier.net users in developing FHIR® implementation guides for their jurisdictions. Useful reading as our NZ approach takes shape, led by the HL7NZ FHIR Implementation Work Group on the FHIR NZ Base project
FHIR NZ Registry on Simplifier.net future support for FHIR R4B and FHIR R5
The national home for locally-produced HL7® FHIR® artefacts