While we are approaching 7.1 release, we still integrate critical bug fixes into 7.0.x branch and here is the latest update for your production servers: 7.0.4 build #21474.
Included are various performance improvements which can affect large TeamCity installations, fixes in Subversion integration and more. See the full list.
There are no data structure changes comparing to 7.0.3, so downgrade to other 7.0.x releases is possible.
Anyway, it's a good time to create backup for your server. The one from Administration > Backup with "Basic" setting is usually enough.
If you want to prepare for upgrade to TeamCity 7.1, consider checking out our last EAP build and let us know how new features work for you.