As far as I know Sitecore is introducing a new serialization in version 9.2, but is this the same as Rainbow serialization?
As you know Rainbow is an open source advanced serialization and comparison system for Sitecore which is using a YAML format.
In Sitecore 9.2 there is a new serialization implemented in a YAML format.
So Rainbow and Sitecore 9.2 both using YAML format, but they are not the same.
Sitecore is not using the Rainbow serialization format!