A lot of people *will* buy Windows 7. Maybe not so many in absolute terms - but MS will buy just enough publicity to make it look like *everyone* is doing it (hell, the launch of XP was the #1 item in the fucking *news* FFS. They probably paid millions for that). Every magazine will be full of 'how cool windows 7 is', every online blog they can buy will be full of 'how to do cool things with windows 7' (and I expect this will include slashdot, since they have feed their families just like everyone else).
A lot will pirate it - and MS are fine with that because if they're using MS products they're not using the competition.
Like it or not, Windows 7 launch will be huge, whether the OS is any good or not.