It depends if you intend to retain Windows 7 as a separate OS on this system as dual boot. If not, then there will be methods to "Upgrade" Win 7 to Windows 8 although I doubt full details have yet been released.
The Windows 8 beta is only for testing purposes and feedback to Microsoft, so I shouldn't expect to save anything from that when it's done. It's a 'throw away' install, and if I remember rightly, the Win 7 beta was time limited anyway. It stopped working after a certain date. I expect Windows 8 beta to be the same.
But the caution is this;
We know that, when installing a newer OS onto a system as dual boot where there is an existing older OS, (example, XP already installed, then install Win 7 as dual boot), the boot file for the older OS gets replaced by the newer versions boot file.
In my example above, older XP already installed then you install Win 7 on a different partition or hdd as dual boot. Win 7 replaces XPs boot.ini with it's own BCD (Boot Configuration Data). The boot.ini file on the XP partition/drive is replaced.by BCD
If that XP install is then removed/reinstalled, or the partition/drive is reformatted, or access to the partition/drive is lost, then you also lose access to the Win 7 OS, because the BCD has gone. It is often very difficult to recover from that and sometimes the only recourse is to reinstall Win 7 from scratch.
So you need to think about this if and when you begin testing Win 8.
And as Bob says, there will be Microsoft forums dedicated to Win 8 testing.
As to transferring settings and personal files, the old maxim is true. We lose what we don't backup.