I don't know, this just hit me today about this subject. Theoretically, OEMs could switch to Linux or android if they wanted to, but what stops them is Windows. Think about this, when vista came out, people had issues with it and hated it and wanted to poo on it. Some did. But even though some OEMs were making PCs with vista that could barely run it, people still stuck to Windows. Granted, people just stuck with xp until the storm was over, then moved onto 7. Even though there was the angst against vista, people still used a Windows product.
But, as we live in different times with different factors, this may or may not turn out the same. The main thing is the Surface. Looking at it, it won't cause any main issues with the OEMs as Microsoft will only sell it in THEIR Microsoft Stores and I believe online. Not a huge market to broadcast it. There is also the hugely different UI with Windows 8, but I don't think that would be a matter as you CAN use it. There isn't a physical impediment to it unlike vista, where you sat there for minutes on end just to open a few programs at the same time.