We are working on migrating our Sitecore instances to Sitecore 9 and we are using xDB for analytics. We read new version of Sitecore does not support MongoDB. Can we still use xDB and analytics?
Sitecore provides the xDB Data Conversion tool that supports xDB data conversion. This tool will help you in migrating the data from Sitecore Experience Database 8.x to Sitecore Experience Database 9.0.
You can download this tool from https://dev.sitecore.net/Downloads/Sitecore_Experience_Platform/90/Sitecore_Experience_Platform_90_Initial_Release.aspx
MongoDB may be supported in future version of Sitecore 9 versions.
You can review more information about tool at https://dev.sitecore.net/Downloads/Sitecore%20xDB%20Data%20Migration%20Tool/2x/xDB%20Data%20Migration%20Tool%2020