Yes. If you buy (or bought) a PC running any edition of Windows 7 other than Starter between June 2012 and January 2013, you can register here to be emailed at the time of General Availability with a promotional code that will allow you to claim your copy of Windows 8 Pro for a mere £14.99 via digital download.
Windows will also be offering DVD versions at a raised cost, but with a significant discount still applied. Owners of digital versions will still be able to create their own recovery media onto either Flash Disk or DVD as with Windows 7. Windows are also allowing you to claim this offer on up to five recently acquired machines per registration, which is generous to say the least.
Simply visit the above link, input a few contact details, chiefly an email address, followed by a few details on your purchase (date of acquisition, retailer and product model etc.) After that, you may sit back and await your discounted version of Windows 8 Pro.
Certainly worth taking five minutes out of your day for.