I think you'd have trouble buying a Mac that doesn't have multitouch support today, considering that Macbooks come with multitouch trackpads and iMacs come with Magic Mouses (with desktop trackpads advertised alongside them).
If the trackpad counts, then virtually every Windows device supports multitouch too. So why is this a reason for Apple to stop supporting Safari on Windows? I don't think it has anything to do with gestures.