Mendix 5.0.0 will be released tomorrow! That version will be able to convert Mendix 4.7.2 projects.
Mendix 4.7.2. was released after 5.0.0-rc1. Therefore it indeed, cannot be converted. The release notes of 5.0.0-rc1 state the following:
Modeler 5.0.0-rc1 can open projects created with Mendix 4.7.1 (was 4.6.1 in 5.0.0-beta8). It includes all fixes and features introduced in Mendix 4 since 4.6.1.
So only projects up to Mendix 4.7.1 can be openend / converted in 5.0.0-rc1.
Probably the next release will be able to convert 4.7.2 projects.