No... in this scenario you would be able to upgrade the VM from Windows 7 to Windows 8 (which obviously is rather pointless).
What you would need is an OEM copy of Windows 8 and Windows 7. OEM copies will be available for purchase October 26th.
Your other option would be to purchase a TechNet subscription which for $199 ($149 to renew after the initial purchase year) gives you 2 licenses for Windows 8 Pro and also gets you A LOT of other Microsoft software including Windows 7, Office 2010 and the soon to be released Office 2013. They've scaled back a lot of what used to be offered in TechNet, and it's STILL a really good deal. Going this route would allow you to get Windows 8 as soon as the subscription is activated which usually takes about 3-4 days.
Do keep in mind that one of the changes recently made was the loss of perpetual evaluation rights. This means that if you allow your subscription to lapse, in addition to losing access to download software from the TechNet website, you will now not be able to activate any new installs of the software offered via the subscription until you renew it. This was possible under the old terms as long as you saved the serial number from the TechNet website. This will not however (let me repeat that.... will NOT) deactivate any existing installs of software using licenses acquired through TechNet.
I've had it for a few years now and I'm really enjoying it. given what you are hoping to do, you may want to take a serious look at it.
On a side note regarding the VM you mentioned, if you are going to have the VM set up for less than 30 days (120 for Windows 7 if you re-arm the activation timer the maximum number of times allowed), you should consider NOT activating the virtual machine, as you do have a limited number of activations with TechNet licenses, just like any other software license from Microsoft.
Oh great... here comes the FUD yet again. This crap really needs to stop. Windows 8 works. Once you take the 20 minutes to get used to the Metro interface that you will use MAYBE 10% of the time you are on a non-touch enabled desktop or laptop computer, I'm betting people will love it.
Microsoft is offering a similar program to students at college or university called Dreamspark - this may be what you were referring to in your last post. Once you register an account with Dreamspark (ISIC Card, verification code from school administration, or verified school email address required for signup) you should be able to get most (if not all... I've never used Dreamspark myself) of the software for free.