Unfortunately no readily available migration path from Confluence. I'm not familiar enough with Confluence myself to understand the formats and options that we'd need to carry across & support.
Our API [1] has recently matured to now support the different content types so that could be utilised for such a migration job although the API is still growing to cover more actions/models.
Have recently been thinking about possibly offering some form of paid service support service to help the process and help fund the project.