It just needs a few tweaks to fix the niggles. Adding a 'launch to desktop' option, putting the shutdown button in a sensible place, reinstating the 'Start' button and having it trigger a side-bar version of the Start page, fixing corner-menu detection and making 'All Programs' easier (and more obvious) to access. Windows 8 can do everything Windows 7 could do (and more). The problem is that the UI change means it's not always obvious how to do it, particularly when on the Desktop. More familiarity is needed to start with; Metro UI use will come as people get used to it on touch devices (and Xbox).
Most devices running new versions of Windows are new devices; only a small percentage of users actually upgrade. As such I'm not sure the current availability of touch screen Windows devices is all that relevant. It's not about what's out there now, but about what OEMs will release later this year. If most Windows 8 PCs are sold with touchscreens then most Windows 8 devices will, in fact, have touch screens.
Also, Vista sold really well. You probably know that, but it's worth remembering. Reputation-wise it did Microsoft no favours, but sales-wise it was definitely a success. If W8 does as well as Vista then it's done it's job; sales of that level would no-doubt mean that most people are used to Metro by the time W9 is released anyway. A couple of minor tweaks later and W9 is hailed as the second coming...