Hi,
there are currently no plans for this. UrBackup is designed for a single storage path. You can use symlinks and the like to redirect clients to a different path – it will work but it will be suboptimal, because clients then cannot share data. So for a lot of data you should go for a raid (5 or something). You have to do that anyways for 5TB data, because there are no 5TB disks.
You can, however, use multiple, independent UrBackup servers. Those would then each have independent backups of the same clients (or you can configure which client should use which server). It should be possible to run multiple instances of the server on the same OS, though nobody has done this before, I think.