There are rumors that Microsoft may be going with a free version of Windows 8. Free, but ad supported. This has worked for many products (Juno ISP, Kindle with ads, etc.). As an OS, I'm not sure how many people would be willing to install an OS with adware already installed. I'm sure there will be a few people, but I'm not sure if it's be enough to continue the support for the free version. Of course, I could be wrong and this could be a huge hit among consumers. 

This new SKU, from what my contacts are saying, is key to Microsoft's experimentation with monetization. I hear this SKU has only minor differences from the current Windows 8.1 SKUs, but that it may be a kind of placeholder for the future when consumer operating systems are, basically, free. I'm not sure if this SKU will offer OEMs and/or consumers new Bing-related incentives by the time Update 1 is made available this spring.