While you could reference a swagger 2.0 doc in the sourceDocuments section, tooling support and some aspects (e.g. operationRef) are going to be dependent on OpenAPI 3.x and later. I would advise migrating to OpenAPI 3.0 or later as it's been out for quite some time now, and there are a variety of tools that can help with that, but if that is not possible, I don't know that you'd want to embrace Arazzo until you have migrated to 3.x or later.

@Sara-cunningham while the OpenAPI community in general encourages everyone to upgrade from OpenAPI v2 to later versions of the OpenAPI Specification (which I believe is the sentiment of @kevinduffey response), remaining on v2 does not stop you from describing use-cases and workflows with Arazzo.

Let me know if you hit any issues, but in general all should be fine.