If you want to move from o365 Hybrid to Cloud only you will have to disable AD Sync, to do this
- Connect to o365 with Powershell
- Disable Microsoft ADsync Service on your Server
- Disable Dirsync with Set-MsolDirSyncEnabled –EnableDirSync $false
- Remove the immutable id with Get-MsolUser -All | Set-MsolUser -ImmutableId “$null”
After that all users should be "in cloud" on the o365 Admin page. The next step would be uninstalling AD Connect from your Server.