Just last week I was bemoaning the fact that neither Parallels nor VMWare Fusion provided an easy way for a developer to create a virtual machine (VM) for testing of OS X Mavericks, so I ended up installing the new Mac operating system on a separate partition. Today Parallels released an update to Parallels Desktop 8 for Mac that not only allows the update of existing OS X VMs to OS X Mavericks, but also allows Mavericks to be a host machine for Parallels.
If there's a downside, it's that you still can't install OS X Mavericks on a blank VM; instead, you'll have to install a previous version of OS X on a virtual machine, then acquire the installer from the Apple Developer Center and upgrade the VM. The update can be applied to an existing install of Parallels Desktop 8 by launching the app and selecting Check for Updates under the Parallels Desktop menu.
As of yet, there's still no word from VMWare on how they're progressing on OS X Mavericks compatibility, but we'll be sure to pass along any information that we hear about.