So I am ready to purchase some Windows 8 Pro licenses for testing, but normally do not purchase software assurance.  Am I going to be left out in the cold if I purchase a VL Windows 8 Pro upgrade today when 8.1 comes out on October 17th since I didn't purchase software assurance?

You will need to contact a Microsoft Volume Licensing Specialist and ask them.

It was announced in this blog post by Brandon LeBlanc on August 14th, 2013 that Windows 8.1 will be available as a free update through the Windows Store on Windows 8 as of October 17th, 2013 at 4:00 AM. With that said, it is my understanding that if you were to purchase a VL Windows 8 Pro upgrade now, your machines with Windows 8 Professional Volume Licenses will be able to receive the free Windows 8.1 update as of that date and time.